Journal for

Occultation
Astronomy
Volume 13 · No. 4 · Rev. 1

Occultation of Alpha Orionis by (319) Leona, 2023 December 122023-04

Dear reader,Almost all solar eclipse chasers go to the centre line to maximise
their enjoyment of nature’s wonderful spectacle. However, a small
number of dedicated observers locate themselves at the northernor southern limit of totality to record the prolonged displays of
Baily’s Beads to estimate the Sun’s diameter. This edition of JOA
contains reports on the solar eclipse of 2023 April 20, where twocollaborating teams obtained accurate timings of the Beadphenomena, recorded photometric data on the changing lightlevels and timed the flash spectrum.

COVER

Cooperation and meetings are the lifeblood of our team ethic
and this is evident in the recent formation of IOTA/EA catering
for occultation observers in East Asia, and the detailed report of
IOTA’s 41st annual meeting.
In September, ESOP 42 in Armagh, Northern Ireland was a mostenjoyable and productive meeting. The keynote session was on
the occultation of Betelgeuse by asteroid (319) Leona on 2023
December 12. The ground track is well defined, but because
Betelgeuse and the asteroid subtend similar diameters this ‘once ina lifetime’ event will most likely be a partial or annular occultation,requiring different techniques to record its high dynamic range.
The comprehensive Call For Observations and Practical Advice
describe how you can participate in this major pro-am campaign.

)

Clear skies,

Alex Pratt
IOTA/ESJOA Volume 13 · No. 4 · Rev. 1 · 2023- 4 $ 5.00 · $ 6.25 OTHER (ISSN 0737-6766)

In this Issue:
6

Copyright Transfer
Any author has to transfer the copyright to IOTA/ES. The copyrightconsists of all rights protected by the worldwide copyright laws, inall languages and forms of communication, including the right tofurnish the article or the abstracts to abstracting and indexing
services, and the right to republish the entire article. IOTA/ES gives
to the author the non-exclusive right of re-publication, but
appropriate credit must be given to JOA. This right allows you topost the published pdf Version of your article on your personal
and/or institutional websites, also on arXiv. Authors can reproduce
parts of the article wherever they want, but they have to ask forpermission from the JOA Editor in Chief. If the request for
permission to do so is granted, the sentence “Reproduced withpermission from Journal for Occultation Astronomy, JOA, ©IOTA/
ES” must be included.

Rules for Authors
In order to optimise the publishing process, certain rules for
authors have been set up how to write an article for JOA. They
can be found in “How to Write an Article for JOA” published inthis JOA issue (2018-3) on page 13. They also can be found on
our webpage at https://www.iota-es.de/how2write_joa.html.

22023- 4 I JOURNAL FOR OCCULTATION ASTRONOMYJournal for

Occultation Astronomy

C A L L F O R O B S E RVAT I O N S :The Occultation of Betelgeuseby (319) Leona on 2023 Dec 12
Mike Kretlow · IAA-CSIC · IOTA/ES · Granada · Spain · kretlow@iaa.es
Jose Luis Ortiz · IAA-CSIC · Granada · Spain · ortiz@iaa.es
Carles Schnabel · Agrupació Astronòmica Sabadell · IOTA/ES · Sabadell · Spain · cschnabel@planetari.cats.

Introduction
Stellar occultations by small Solar System objects like asteroids
are usually intended to study the occulting bodies. However,this technique can also be applied to study the occulted body,i.e. the target star. Historically, high cadence observations(photometer, high-speed imaging) of total lunar occultations ofstars were performed to study the stars, for example to measure
the angular size and/or to resolve close companions. Of course
this limits the ensemble of potential targets to stars lying within
the apparent path of the Moon in thesky. But stellar occultations by asteroids,
in general used to explore the asteroids
themselves, have also been successfully
applied in the past years to study thetarget stars [1, and references therein].

In December of this year, we will have the rare opportunity toobserve an asteroidal occultation of one of the brightest stars in
the northern night sky, the well-known ‘shoulder star‘ of Orion:
Betelgeuse (Figure 1).
Betelgeuse (α Orionis, HD 39801, HIP 27989) is a prominent red
supergiant star (spectral type M1-M2) located in the constellation
Orion. It has roughly 10 times the mass of our Sun and is hugecompared to our central star – about 1,400 times larger, so that
our Solar System up to the orbit of Jupiter would fit into thisFigure 1. In this view, the usual appearance of Orion (left, in an image taken on
2012 February 22), is compared with animage taken on 2020 February 21 (right),
clearly showing the unusual dimming of
the red giant star. Both images were takenwith identical setups and exposure data:
Each is a 30 second exposure taken witha Canon EOS 550D camera at ISO 3200,
17mm f/2.8 lens, Cokin P830 diffuser,
tracked with the Vixen Polarie star tracker.
Credit: H. Raab and Wikipedia
CCBYSA-4.0 : https://commons.wikimedia.org/wiki/
File:Betelgeuse.jpg

JOURNAL FOR OCCULTATION ASTRONOMY I 2023- 43

a lotV-mag: 0.5
U-B: 2.06
B-V: 1.85
Variability : ~0.3 − 1.2 mag
Temperature : 3650 ± 50 K
Spectral type : M1-M2 (Ia-Iab)Radial velocity : +21.91 ± 0.51 km/s
Angular diameter : 42.05 ± 0.05 mas (2.28−2.31 μm)
Angular diam. : 43.15 ± 0.50 mas (1.65 μm, H-band; limb-darkened disk)
Angular diameter : 125 ± 5 mas (2500 Å, continuum)
Distance : 153 (+22,−17) pc; 168.1 (+27.5,−14.9) pc; 222 (+48−34) pc
Radius : 764 (+116,−62) R_Sun; 996 (+215,−153) R_Sun
Periodicity (fundamental) : 388 ± 30 days; 385 ± 20 days; 420 days
Secondary period : 2050 ± 460 days; 2229.8 ± 6 days

Table 1. Fundamental parameters of Betelgeuse
References: [2] and Wikipedia [en]Figure 3: The visual (V band) lightcurve ofBetelgeuse over the past 10 years showing
the prominent dimming of about 1 mag
during January and February 2020. Plot
generated with the AAVSO lightcurve
generator. https://www.aavso.org/LCGv2/

42023- 4 I JOURNAL FOR OCCULTATION ASTRONOMY

Figure 2. In the millimetre continuum Betelgeuse is around 1,400
times larger than our Sun. Betelgeuse would engulf all four
terrestrial planets - Mercury, Venus, Earth and Mars - and even thegas giant Jupiter; only Saturn would be beyond its surface. Image
credit: ALMA / ESO / NAOJ / NRAO / E. O’Gorman / P. Kervella.
 theJournal for

Occultation Astronomy(319) Leona is an outer main-belt asteroid (semi-major axis
a_=_3.4 au), orbiting around the Sun in about 6.3 yrs. Radiometricdiameter estimates (methodically assuming a sphere) reported in
the literature are 40 km [5], 66 km [6], and 89 km [7], to mention
the lower and higher extremes, and a middle value which also
agrees with a count peak in the MP3C database [8].

.

The 2023 Sep 13 and 16 Occultations

In 2010 two single-chord occultations were observed from
Australia and from Japan, with chord lengths of ~44 km [9] and~35 km [10]. But these single-chord occultations are not sufficient
to constrain the diameter of (319) Leona or even to tell us
something about the shape. For that reason and in preparation for
the Betelgeuse event, a special campaign to detect multi-chord
occultations by (319) Leona was carefully planned. Results fromoccultations observed on 2023 Sep 13 (Spain and Portugal) with
19 positive detections and Sep 16 (USA) with 3 positive detections
indicate that roughly the middle value of about 66 km seems to
be a realistic estimate for the mean size of (319) Leona. Thus, it
is reasonable to use this value for the occultation predictions.
In the ALCDEF and LCDB light curve databases [11, 12] we findrotation periods of P ~52h (Behrend 2016+2023), P ~14.9h(Alkema 2013) and P1 ~430h / P2 ~1080 h (Pilcher et al. 2017)1, 2.
The reported light curve amplitudes are in the order of 0.5 - 0.65
mag. Yet no 3D model of (319) Leona exists in the DAMIT database[13]. However, Durech [14] very recently published a preliminary
physical model, by combining the published light curve data from
Pilcher et al. (2017) with sparse photometric data from ATLAS
and Gaia DR3, confirming a tumbling state, but with periods ofP1 ~314 h (rotation) and P2 ~1172 h (precession).
 References given in ALCDEF & LCDB.

Figure 4. Ellipse fit to the chords of
the Sep 13 occultation observed in
Spain and Portugal, projected on the
Besselian fundamental plane. The
black part and the start and end of
the chords are the timings uncertainties derived from the light curvefit. The used time source is given inparentheses after the observing site
designation. The projected surface
equivalent diameter is 65-66 km.

JOURNAL FOR OCCULTATION ASTRONOMY I 2023- 4

5.

Further Occultations
Before Dec 12

Figure 5. Ellipse fit to the chords of the Sep 16 occultation observed in the USA (AZ),
projected on the Besselian fundamental plane. The black part and the start and end of
the chords are the timings uncertainties derived from the light curve fit. The used timesource is given in parentheses after the observing site designation. The mean projected
size of the ellipse is 55 km. The shaded grey zone is the 3-sigma uncertainty region of
the fit. This result (size and orientation of the ellipse) would still be in agreement withthe fit in Figure 4 within the parameter uncertainty.
d The 2023 Dec 12 Occultation

Figure 6a.

62023- 4 I JOURNAL FOR OCCULTATION ASTRONOMYJournal for

Occultation Astronomy

Figure 6b.

Figure 6c. Predicted central (total) occultation shadow path of (319) Leona on 2023 Dec 12. Not shown is the region of partial occultation
which extends perpendicular to the path. JPL#69 ephemeris was used for (319) Leona. The position of Betelgeuse was computed by using
the epoch 2017.0 position from the USNO-UBAD catalogue [24] and the proper motions were taken from [25]. An interactive online map
is provided at [22]. Map created using the OpenStreetMap data service.
lues.

track direction, which by chance is not that far away from thesituation we have had at the Sep 13 occultation. In Figure 8 weshow simulated occultation light curves for these values.

Figure 7. Predicted profile and orientation (blue line) of (319) Leonafor the Dec 12 Betelgeuse occultation (Durech [14]) on the sky plane.
The grey shaded ellipse is visually fitted to that profile.The size ofthat ellipse is 74 x 57 km (projected surface equivalent diameter~65 km), with rotation angle φ ~ 25°.

JOURNAL FOR OCCULTATION ASTRONOMY I 2023- 47alternative possibility is to modify a (3x) multi-image
filter prism trick lens with colour filter inlays in orderto get three different-colour images of the star at thesame time [29]. Due to the high dynamic range of theevent (measuring the gradual occultation light curve ofa bright star), detectors with high dynamic range andresolution (bit depth) should be preferred.
Also, consider the drift scan technique (DRS) [30],which is especially suitable for this event because of
the brightness of the star. It does not require sidereal
tracking, so a camera on a tripod is sufficient. It also
simplifies somehow the demands on timekeeping, as
only one single image needs to be timed. The program
Scanalyzer can be used to reduce such a sometenseconds-exposure drift-scan image.
Finally, another observing aim would be to do highresolution spectroscopy. Though there are also amateurs and pro-am groups working in this domain, we
do not go into details here and refer to web resources
and special information (also given at the end of thearticle) covering that topic.

Figure 8. Simulated display (on the sky plane) and light curves of the Betelgeuse
occultation using an ellipse for (319) Leona with values given in Figure 7 anda diameter of 50 mas for Betelgeuse. Three different situations are shown: (a)observer on the central line, (b) 30 km south of observer (a), and (c) 30 km
north of observer (a). In each case the asteroid is moving horizontally fromleft to right. In the upper panel the view at mid-occultation (for that site) isshown. The plot with the corresponding light curves in the lower panel shows
the normalized intensity vs time t-t0 in seconds, where t0 is the mid-occultation
time for the observer on the central line (case a), thus cases b and c are
shifted.
Graphic and light curves created with https://starblink.org/occult_simulator_enns.

Conclusion

The occultation of the supergiant star Betelgeuse will be
an extremely rare and amazing event, happening overa densely populated region. It will give the opportunity
not only to eyewitness a spectacular astronomical
phenomenon, but also to contribute to sophisticatedscientific observations and projects with rather simple
means. We can also expect that this event gives an
excellent opportunity for citizen science projects andpro-am collaborations and thus to enhance the visibilityof public observatories and astronomical associations.
We recommend potential observers to frequently
consult the web resources given at the end of this article, social
media and/or to contact the authors about dedicated projects
and campaigns in different regions. Regional IOTA coordinators
can also be contacted to get involved in specific campaigns.

References[1] https://iota-es.de/esop39/lections/richichi-esop39.pdf[2] Dupree, A. K. et al., 2022. The Great Dimming of Betelgeuse: A
Surface Mass Ejection and Its Consequences. The Astrophysical Journal,
vol. 936, 18, doi: 10.3847/1538-4357/ac7853.
[3] https://www.eso.org/public/news/eso2109/[4] Karovska, M., Nisenson, P., and Noyes, R., 1986. On the alpha Orionis
triple system. ApJ, vol. 308, 260, doi: 10.1086/164497.
[5] Masiero, J. R., et al., 2014. MAIN-BELT ASTEROIDS WITH WISE/NEOWISE: NEAR-INFRARED ALBEDOS. ApJ, vol. 791, no. 2, 121,
doi: 10.1088/0004-637X/791/2/121 .

8

2023- 4 I JOURNAL FOR OCCULTATION ASTRONOMYJournal for

Occultation Astronomy[6] Usui, F., et al., 2011. Asteroid Catalog Using AKARI: AKARI/IRC MidInfrared Asteroid Survey. Publications of the Astronomical Society ofJapan, vol. 63, no. 5, 1117–1138, doi: 10.1093/pasj/63.5.1117.
[7] Nugent, C. R., et al., 2016. NEOWISE REACTIVATION MISSION YEAR
TWO: ASTEROID DIAMETERS AND ALBEDOS. The Astronomical Journal,
vol. 152, no. 3, 63, doi: 10.3847/0004-6256/152/3/63.
[8] https://mp3c.oca.eu/bodies/Leona/ (queried on 2023-09-30)[9] https://astro.kretlow.de/cora/events/occult/2010-10-22/
UCAC4%20480-003465/(319)%20Leona/[10] https://astro.kretlow.de/cora/events/occult/2010-10-27/
Tycho2%200045-01477-1/(319)%20Leona/[11] https://alcdef.org/ (queried on 2023-09-30)[12] https://minplanobs.org/mpinfo/php/lcdb.php (queried on
2023-09-30)[13] https://astro.troja.mff.cuni.cz/projects/damit/ (queried on
2023-09-30)[14] https://sirrah.troja.mff.cuni.cz/~durech/Leona/ (queried on
2023-10-10)

Web Resources
https://www.armagh.space/site/wp-content/uploads/2023/02/beisker_analyser_1.pdf[15] Ortiz, J. L., et al., The stellar occultation by (319) Leona on 13
September 2023 in preparation for the occultation of Betelgeuse. arXiv,
21-Sep-2023, doi: 10.48550/arXiv.2309.12272.
[16] https://astro.kretlow.de/cora/events/cora/2023-09-13/
GDR3%203347400001862704896/(319)%20Leona/[17] https://astro.kretlow.de/cora/occultations/53a66098-eafc-4c28b31e-27fb3988a904/[18] https://astro.kretlow.de/cora/occultations/5dfd8280-0694-4bc3a0e0-a582dcb91956/[19] https://astro.kretlow.de/cora/occultations/
5ef04740-02a3-430a-958e-a74d923e4e60/[20] https://astro.kretlow.de/cora/occultations/8707774a-f497-4de8a38d-c6b885e6f027/[21] https://astro.kretlow.de/cora/occultations/
8ae06798-0072-438ea21c-ede92198fd59/[22] https://astro.kretlow.de/cora/occultations/aa3579fb-2fa7-4a89-8452-bfc8a87e0704/[23] https://lesia.obspm.fr/lucky-star/occ.php?p=124370[24] Munn, J. A., et al., 2022. Accurate Ground-based Astrometry ofNaked-eye Stars: The United States Naval Observatory Bright-star
Astrometric Database. AJ, vol. 163, no. 3, 131,
doi: 10.3847/1538-3881/ac41d2.
[25] Harper, G. M., et al., 2017. An Updated 2017 Astrometric Solution
for Betelgeuse. AJ, vol. 154, no. 1, 11, doi: 10.3847/1538-3881/aa6ff9.
[26] https://en.wikipedia.org/wiki/
Betelgeuse#Table_of_angular_diameter_estimates[27] Couto, E., Occult Flash Tag https://apkpure.com/es/occult-flashtag/
br.eti.erickcouto.occultflashtag/versions[28] Grismore, J., AstroFlashTimer, https://sites.google.com/site/
astroflashtimer/home[29] https://astrode.de/esop23c.htm[30] Broughton, J., Drift-Scan Timing of Asteroid Occultations,
https://www.asteroidoccultation.com/observations/DriftScan/Index.htm

JOURNAL FOR OCCULTATION ASTRONOMY I 2023- 4

9Practical Advice for the Occultation of
Betelgeuse by (319) Leona
Carles Schnabel · Agrupació Astronòmica Sabadell · IOTA/ES · Sabadell · Spain · cschnabel@planetari.cat

ABSTRACT: On the night of December 11-12 this year, the minor planet (319) Leona will occult
Alpha Orionis (Betelgeuse) for a maximum of 12 seconds. As a very gradual fall and rise of thelight level is expected, special techniques will need to be applied on this occasion. But, as always,
accuracy in timing and position of the observer are crucial. In this article we try to provide sometips in order to get the most out of this unique phenomenon.
Introduction
As Mike Kretlow explains in another article on pages 3 - 9 in thissame issue, this event will have some unusual features. We will
be exposed to a continuous variation in light level in an intervalof only a few seconds. Also, it seems that the shape of the light
curve will look different depending on the wavelength.
In this occultation, as in any other, it is important to obtain agood signal-to-noise ratio so that there is no doubt as to whether
the star is occulted or not, and a good temporal resolution inorder to be able to evaluate the occultation time with sufficientprecision to coordinate all the recordings altogether. It is essentialthat both the timebase and the geographical location of theobserver be highly accurate.

What Equipment Can Or Should Be Used?
If using a telescope with a small field of view, it is advisable touse a tracking mount. You can't waste time recentring for aphenomenon that only lasts a few seconds. However, given thebrightness of Betelgeuse, a short focal length photographic lens
will also be useful. In this way, we will be able to include stars
with similar brightness to that of Betelgeuse in the same field.
With short focal lengths tracking will not be necessary.

Imaging
Regarding the camera for recording the occultation, there areseveral options:
On the one hand, you can have an analogue video camera,such as the Watec 910 HX-RC [1] used for recording stellar
occultations by asteroids, whose analogue signal is going througha time inserter controlled by GPS, such as, for example, the IOTAVTI [2], which allows time to be stamped with a precision of
thousandths of a second in each frame. This analogue signal isinjected into an analogue-digital converter that allows the signal
to be read with the computer to be recorded in AVI format, forexample. An advantage of this type of camera is the recordingof 25 images per second (PAL version) or, if analysed properly,

102023- 4 I JOURNAL FOR OCCULTATION ASTRONOMY

even 50 images per second. The resulting exposure time is 40
milliseconds per frame, or 20 if what we analyse are the fields.
Each frame has two fields.
This is the system used for many years by many occultation
observers, but a problem that appears in this method is that thedigitization is carried out with only 8 bits (256 grey levels) and thenoise is relatively high. In a normal occultation the star disappears
completely for a more or less long period of time, but in thiscase the fall will be gradual. Would the occultation be recorded?
Surely yes, but perhaps not all the science can be obtained fromthe observation with the previous instrumental configuration.
Other equipment available today would use a digital camera
equipped with a GPS module to obtain a reliable time. An
example is the QHY174M-GPS [3], which gives the time of each
image obtained with the appropriate precision. At best thiscamera records in 12-bit mode, 4096 levels of grey, scaled to 16bit output, but that could already be enough in this case. As fornoise, according to specifications, it ranges from 1.6 to 5.3 e-,depending on the gain used. In addition, it allows you to obtain
continuous images with a significant cadence. The DVTI+CAM[4] is another similar camera with GPS time insertion.
Other CMOS or CCD cameras can also be used, with 12 or better,
16 bits, although fast cadences must be achieved, from 10 to 40
images per second, and short exposure times, on the order of afew milliseconds, without dead times between them.
Betelgeuse is a bright star and its images in your recording mustnot be over-exposed. Take care to avoid image saturation before,
during and after the occultation. A camera with a high dynamic
range (12-bit or more) is preferred. Some cameras running atvery high frame rates might reduce their quality setting from 12bit to 10-bit.
Test your equipment before the event!

Journal for

Occultation Astronomy

Timing
The most important problem with cameras of this type is that
their recording is not referencing an exact and precise time base,since the computer clock has fluctuations that can spoil theobservation. A solution to this problem is to continuously andsystematically update the computer's clock with GPS systems or
use an NTP (Network Time Protocol) server. The recommended
application that can do this for computers with Microsoft
Windows_10 operating systems and higher can be found at
Meinberg [5, 6].
If you do not have access to GPS systems or NTP timing you
can use smartphone apps to flash at synchronised time intervals.
(See this issue, page 8).

Filters & Spectroscopy
At this point we have to define what filters to use. The simplest
case would be to apply standard photometric filters, B and/or V
from Johnson, Cousins R, or the Sloan b, g, r filters [7]. Narrow
band filters can also be used in H-alpha, or in the titanium oxideline to see how these lines vary during occultation. Once theobservation is finished, calibration images must be obtained, thatis, bias, dark and flat shots.
A separate point would be to perform spectroscopy with hightemporal and, if possible, also spectral resolution. More and more
people in the amateur world have spectrographs and could try
to make this type of observation. But what we have said before
is required, short exposures and very precise time base.
A very interesting proposal about fast spectroscopy wassuggested by Wolfgang Beisker during the last ESOP 42 held in
Armagh [8]. It consists of a slitless spectrograph equipped witha low-resolution blazed grating with 100 grooves per mm. In
this case the wavelengths to be used can be selected after theobservation. The resolution of such a setup can be improved byputting a prism before the passage of the starlight through thediffraction grating.

Analysis
Regarding photometric analysis, there are different freeprograms that can be used. Among those specialised in occultations we have two: Tangra, by Hristo Pavlov [9] or PyMovie and
PyOTE by Bob Anderson [10]. Obviously, when used for the firsttime they are not easy, but, with a little practice, they are very
useful for this type of observation. A program that could also be
used is Julio Castellano's, Fotodif [11], well-known in the Spanish
speaking world.

Collaboration Is Needed
The heterogeneity in the different recording methods can create
problems when calibrating the registration times with each other.
In normal occultations contacts are easily recognised as they are
abrupt photometric changes. With Betelgeuse the light variations
will be gradual, whether we do white light photometry or throughdifferent filters. Changes in the spectra will also be gradual. Anotherproblem is the field of view. If it is of the usual amplitude, we will
not have stars for comparison. For these and other reasons, it will
be highly advisable to combine different types of recordings at thesame observation station: photometry with and without filters, withwide and narrow fields of view, but above all well-synchronised intime, can be an indispensable support for teams that are
performing spectrometry in the same place, but do not haveprecise timing control.
So, the advice is to be attentive to the different teams that aregoing to join forces to observe. The different regional teams along
the path of the occultation are using the Planoccult mailing list
[12] to announce the different coordination initiatives and online
meetings. Please also announce the expected location of yourstation in Occult Watcher [13]. If you are interested in observing
this event, please join us!

References[1] http://www.watec-shop.com/en/products/monochrome-cameras/
wat-910hx-rc-remote-9.html[2] https://occultations.org/observing/recommended-equipment/
iotavti/[3] https://www.qhyccd.com/qhy174gps-imx174-scientific-cooled-camera/[4] https://dvticam.com/home[5] https://www.meinbergglobal.com/[6] Pavlov, H., Gault, D., Using the Windows Clock with Network Time
Protocol (NTP) for Occultation Timing, Journal for Occultation
Astronomy, 2020-02, p. 10-19[7] https://www.baader-planetarium.com/en/filters/photometricfilters.html[8] Beisker, W. , Fast Spectroscopy with a Slitless Spectrograph – Using aBlazed Grating with Low Resolution (link updated on 2023 Oct 31)
https://s3.eu-west-1.wasabisys.com/armagh.space/site/wp-content/
uploads/2023/02/19132154/beisker_analyser_1.pdf[9] Pavlov, H., Tangra, http://www.hristopavlov.net/Tangra3/[10] Anderson, B., PyMovie
https://occultations.org/observing/software/pymovie/[11] Castellano, J., Fotodif, http://www.astrosurf.com/orodeno/fotodif/[12] Planoccult mailing list
https://lists.vvs.be/postorius/lists/planoccult.ls.vvs.be/[13] Pavlov, H., Occult Watcher, https://www.occultwatcher.net/

There are certainly other free or commercial programs that canbe used, but here we have pointed out the most common onesin this field.

JOURNAL FOR OCCULTATION ASTRONOMY I 2023- 4

11

Baily's Beads Observation during the Hybrid
Solar Eclipse 2023 April 20
Konrad Guhl · IOTA/ES · Berlin · Germany · kguhl@@astw.de

ABSTRACT: The timing of Baily’s Beads, observed during a solar eclipse is one of the mostaccurate ground-based methods for estimating the solar radius. In 2023, IOTA/ES organised an
expedition to the northern edge of the total part of the hybrid solar eclipse (TSE) on April 20,
where bead observation was possible. The timing was measured by photometry in FITS files. The
correction to the solar radius of Δ Rs = 0.38” was derived from this observation.
Introductionlity.

Eclipse Parameters and Observation Site

Figure 1. Area of visibility for the eclipse [2].

Figure 2. Eclipse zone in Cape Range National Park [3].

122023- 4 I JOURNAL FOR OCCULTATION ASTRONOMYJournal for

Occultation Astronomy

Northern Station 2023AUN1(Elke & Konrad Guhl)
The northern station was located in the Cape Range National
Park. The observation location (Latitude 22° 00’ 22.4” S; Longitude
113° 56’ 15.3” E; h=3 m (WGS84)) was within the totality zone
and the predicted length of totality was 31.5 s [3], (Figure 3).

Like former TSE and ASE observations, the optical equipmentused follows the IOTA/ES recommendation. It is based on a
100/1000 mm Maksutov optic, a 535 nm filter and the IOTA/ES
solar filter. After reduction TSE020720219 [4] the type of camera
used was changed: A 12-bit digital camera QHY174MGPS was used
to record a series of images in FITS format. The time protocol isdone by timestamps in the FITS file by GPS synchronisation.
Following the station code created in [5], the station is called
2023AUN1.

Figure 4. FITS image of Baily's Beads visible on the lunar limb at
03h 30m 07.18s UTC.

Reduction Method and Results

Figure 3. The author at the set-up station with 100/1000 Maksutovon a travel mount and a camera QHY174M-GPS. In his hand thecontrol-box for the fine adjustment of the drive of the mount, on
the monitor the Sun as a crescent. (Photo: Elke Guhl)

All observations were simulated with the software tool ”Baily
Bead Analysis“ of the software Occult [6]. The version V 4.2023.9.26
includes the LOLA data for the lunar limb profile.
Figure 5 shows the simulation for the axis angle 278° till 296°with a radius correction of 0.38“ and image scale 4.0. The time
for this simulation is 03h 30m 08.2s UTC.

Figure 5. Simulation in Occult.

JOURNAL FOR OCCULTATION ASTRONOMY I 2023- 4

13

ed. 

e 4). 

Figure 7. Light curve disappearing bead at AA=98.3

Figure 8. Brightness profile along the solar radius, station 2023AUN1.

142023- 4 I JOURNAL FOR OCCULTATION ASTRONOMYJournal for

Occultation Astronomy

All data points, following the method described above, arepresented in table 1 Following the data table format of [5]:2023AUN1

Acknowledgements
The author thanks M. Xavier Jubier for the fruitful e-maildiscussion in the planning phase of all expeditions from the author
and the helpful web page. Further thanks are hereby extended toLuca Quaglia for on-site organisation and collegial discussions,and to John Irwin for supportive calculations.

Time
UTC

Axis
Angle

Type

Variation Solar
Radius Δ rS

03:28:52.7

99.3°

D

0.55”

03:28:52.9

98.3°

D

0.60”

03:29:00.4

90.3°

D

0.32”

03:29:00.9

89.0°

D

0.25”

03:29:18.6

67.2°

D

0.37”

03:29:23.3

55.1°

D

0.48”

03:29:25.9

50.8°

D

0.39”

03:29:27.4

48.3°

D

0.34”

03:29:28.1

47.3°

D

0.61”

[6] Herald, D., WinOccult V 4.5.3.0. software tool

08:29:29.2

41.3°

D

0.33”

[7] Dierks, J., Fitswork software tool

03:29:58.0

324.8°

R

0.34”

https://www.fitswork.de/software/

03:29:59.1

330.8°

R

0.31”

03:30:01.2

322.3°

R

0.33”

03:30:05.1

295.1°

R

0.35”

03:30:05.1

282.5°

R

0.30”

03:30:05.7

308.8°

R

0.24”

Table 1.
Data-points, D=Disappearance; R=Reappearance

References[1] Quaglia, L. et.al., Estimating the Eclipse Solar Radius from FlashSpectrum Videos, JOA 2022-2[2] Espenak, F., NASA, https://eclipse.gsfc.nasa.gov/eclipse.html[3] Jubier; X., Travel and eclipse site, http://xjubier.free.fr/[4] Guhl, K., Baily's Beads Observation During the Total Solar Eclipse
2019 July 02, JOA 2020-02[5] Sigismondi, C. et. al., Baily's Beads Atlas in 2005 - 2008 Eclipses, Solar
Physics, Volume 258, Issue 2, pp 191-202.

[8] Rozelot, J. P. et.al., A brief history of the solar diametermeasurements - a critical quality assessment of the existing data, Proc.
International conference on "Variability of the Sun and sun-like stars:
from astroseismology to space weather", Baku, Azerbaijan, 6 - 8 July
2015, https://www.researchgate.net/publication/307984954[9] Guhl, K., Tegtmeier, A., Baily's Beads observation during the annularsolar eclipse 2016 Sept. 1, JOA 2016-04[10] Guhl, K., A. Tegtmeier, A., Baily's Beads observation during the Total
Solar Eclipse 2017 August 21, JOA 2018-03

The registered third contact was the reappearance of bead
AA=324.8° at 03h 29m 58.0s UTC.

Conclusion
The value adopted by the IAU General Assemblies in Beijing(2012) and Honolulu (2015) for the Astronomical Unit is
1_AU_=_149, 597870700 m exactly and for the solar radiusRʘ_=_6.957 * 108 m. Calculated in arcseconds, the radius is now
fixed to 959.22”.
In [8], the average of the measured solar radius by eclipse observation in 2010, 2012, 2013, and 2015 is given as 959.99_+/-0.06”.
 The solar radius used in [6] is 959.63”.
 In [9] the observed Δ rs is -0.04” for September 2016.
 In [10] the observed Δ rs is +0.03” for August 2017.
 In [4] the observed Δ rs is -0.08” for July 2019.
The average value for Δ rs station 2023AUN1 is 0.38” in 535nm
wavelength. The reduction is done with [6], so the correctedsolar radius is959.63” + 0.38” = 960.01” +/- 0.12

JOURNAL FOR OCCULTATION ASTRONOMY I 2023- 4

15

ATSE2023: Using Photodiode Loggers to
Estimate the Eclipse Solar Radius
Luca Quaglia · Sydney, New South Wales · Australia · besselianelements@gmail.com
John Irwin · Guildford, England · United Kingdom · john@jir1667.plus.com
Alessandro Pessi · Milan · Italy · issepela@gmail.com
Lucian Kafka ·Sydney · New South Wales · Australia · luci@unifiedreality.org
Konstantinos Emmanouilidis · Thessaloniki · Greece · conemmil@gmail.com

ABSTRACT: During the 2023 April 20th annular-total solar eclipse (ATSE2023), we estimated theeclipse solar radius to be Sꙩ ≈ 960.25” by analysing ambient light curves collected with photodiodeloggers and to be 959.90” < Sꙩ < 960.02” from visual observation of the eclipse flash spectrum.
We discuss the apparent discrepancy between these two results and suggest possible causes
which highlight the limitations of using ambient light curves to estimate the eclipse solar radius.

Introductionk.  The campsite  was  rather  Observation Site
Figure 1. Duration of totality as a function of the eclipse solar
radius Sꙩ for a site very close to the umbral shadow path's northern
limit for ATSE2023. The bend in the plot is due to a change in theposition of the lunar limb valley producing third contact.
basic, with no water or electricity, but besides being in a truly idyllic
location, it was absolutely the best we could have hoped for as it
sat less than a couple of hundred metres from the northern limitof the eclipse. We could not have asked for anything better. Figure
2 shows the location of the Mesa campground and the threesites where photodiode loggers were deployed. Also shown are
the theoretical northern path limit lines accurately computed forvarious values of the eclipse solar radius. The WGS84 coordinatesof the three sites were:Site 1Site 2Site 3162023- 4 I JOURNAL FOR OCCULTATION ASTRONOMY

λ113° 56’ 14.7” E
113° 56’ 09.9” E
113° 55’ 31.8” E

φ
22° 00’ 22.5” S
22° 00’ 44.6” S
22° 01’ 43.1” S

h
-1 m
-8 m
-9 m

Journal for

Occultation Astronomy)

Limb Dynamics. 

tively Figure 3. Dynamics around thetimes of second and third contact(C2 and C3) of the solar limb withrespect to the lunar limb for Site 1
and for an assumed eclipse solar
radius of 959.95”. Also indicated
are the lunar valleys where second
and third contact occur.

JOURNAL FOR OCCULTATION ASTRONOMY I 2023- 4

17

Method #1:
Visual Observations and UTC Event Timer
The eclipse was observed by eye through diffraction grating
glasses (Rainbow Symphony Diffraction Grating Glasses 1000_lines/mm) to have a simultaneous view of the white light image ofthe eclipse and its evolving flash spectrum. This view of the flash
spectrum was very sharp. To collect contact times manually webuilt a device able to record the UTC time when a button ispressed. We observed the disappearance/reappearance of thephotospheric continuum in the flash spectrum to determine
approximate contact times.

Method #2:
Photodiode Loggers
The photodiode loggers were designed and built to provide
similar capabilities and functionalities as the loggers describedin [1]. Each logger needs to run autonomously and be able torepeatedly and continuously:
1. Acquire a light intensity measurement.
2. Accurately time-stamp the measurement with UTC.
3. Store the measurement for later retrieval.
We based the design of the loggers
around the Arduino UNO Rev3
board. The board is very practical as
it provides, in an already assembled
package,amicrocontroller(ATmega328P) and a series of digital
and analogue I/O's. Code is written ina dialect of the C programming
language, and it is embedded in the
microcontroller's flash memory.
The photodiode sensor used in theloggersistheHamamatsu
S16838-01MS Si photodiode. It has aspectral sensitivity from 320 nm to730 nm, a peak sensitivity at 560 nm,
and a low dark current. We chose thisphotodiode for its good spectral
response in the visible range. As solar
radius measurements need to be
conducted at a specific wavelength,
light is filtered before reaching the
Figure 4. Photodiode logger deployedat Site 2. The logger was laid
horizontally and kept secured bystones piled up around it as it wasquite windy at the start of the eclipse
partial phase.

182023- 4 I JOURNAL FOR OCCULTATION ASTRONOMY

photodiode surface by using a Player One 1.25” Photospherenarrowband filter centred at 540 nm and with 10 nm bandwidth.
The filter also functions to eliminate as much as possible the lightcoming from the main emission lines of the chromosphere. These
are due to hydrogen (656.3 nm, 486.1 nm, 434.0 nm, 410.1_nm),
helium (587.5 nm, 537.0 nm), magnesium (518.4 nm, 517.3 nm,
516.7 nm), and sodium (589.6 nm, 589.0 nm). The very lowest
layers of the chromosphere (sometimes called the mesosphereor fluctosphere) very near the photosphere also emit a forest of
faint lines that resembles a pseudo-continuum, some of which will
make it through the filter. Albeit faint, light is also emitted fromthe solar corona noticeably at 530.3 nm due to highly ionised
iron (Fe XIV).
Accurate time-stamping is based on the 1PPS signal and on
the NMEA sentences generated by a GPS module. The 1PPS signal
is a train of 100 ms square waves, the leading edges of which
are synchronised to better than 100 ns to the start of every UTC
second. The NMEA sentence allows labelling of the time. The timestamping also relies on the microcontroller's internal oscillator
being disciplined, in code, by the 1PPS signal. The overall time
accuracy of the system is around 1 ms, which is sufficient for theneeds of data acquisition as light intensities around the time of
totality change substantially only over time frames longer than
1_ms.

Journal for

Occultation Astronomy

Data were saved onto a fast SD card. We used the Adafruit
Ultimate GPS Logger Shield to provide the microcontroller's accessto a GPS module and an SD card module. The shield also comeswith a small development area that was used to lodge a level
shifter to boost the 1PPS signal for better detection and ananalogue-to-digital converter (ADC) to measure the photodiodesignal. The ADC we used was a DFRobot Fermion MCP3424 18-Bit
ADC-4 Channel with Programmable Gain Amplifier. Light
intensities vary by over 4 orders of magnitude during a total solar
eclipse - about 2 orders of magnitude from the onset of theeclipse to just a couple of minutes before second contact, thenanother 2 orders of magnitude in the last couple of minutes
before totality. Thus, the ADC needs to provide sufficient
resolution at the lowest light levels as they are the ones in which
we are most interested. There are faster ADCs available, withhigher resolution, but the DFRobot was easy to source and alreadyassembled. Retrospectively, a more performant ADC would havebeen beneficial.

Synthetic Light Curve Computations
Synthetic light curves were computed by integrating the Limb
Darkening Function (LDF) over the exposed area of photosphere.
These synthetic light curves were then fitted over the measured
light curves to infer an estimate of the eclipse solar radius.
Underlying most of this procedure is a detailed eclipse computational model. The model relies on the latest ephemerides andaccounts in a very precise way for all the complexity of the lunar
topography and the orientation of the celestial and terrestrialreference systems via robust algorithms and procedures. Detailsof the model can be found in [2].
The LDF is the one described in [3], where φ is the angulardistance from the Sun’s centre, λ is the wavelength (in μm) andΣꙩ is the topocentric solar semidiameter (directly related to theeclipse solar radius Sꙩ):The integration of the LDF over the area of exposed
photosphere was performed numerically. We used two
independent techniques to ensure the results were correct. The
LDF is normalised to 1 at the Sun’s centre so a suitable linear
transformation is required to match the scales of the synthetic
and observed light curves.

(e.g., an inflection point in the photosphere). We believe,
nevertheless, that Sꙩ is useful as an appropriate parameter to be
used in eclipse computations to reproduce the visual experienceof the eclipse.

Visual Aspect of the Eclipse
The appearance of the totally eclipsed Sun in the sky was very
striking and unlike anything we had ever observed before. Whenthe last Baily’s beads vanished and totality started (confirmed byextinction of the photospheric continuum in the flash spectrum that
we were observing in parallel through diffraction grating
spectacles), the outer corona did not become visible, but the whole
lunar limb was surrounded by a thin ring of very intense light. The
eclipse looked more like an incredibly thin annular eclipse than atotal eclipse. This view of the eclipse was very surprising andunexpected. Anecdotally, some people who sat on the sand dunes
just west of the Mesa campground and some rangers who
observed from Vlamingh Lighthouse (both locations marginallyoutside totality) also described this bright ring all around the Moonas their main experience of the eclipse.
A thought we had on the day of the eclipse was that theappearance of the totally eclipsed Sun reminded us of thedescription that astronomer Clavius gave of an annular-total
eclipse he observed in Rome in 1567 [4]. Modern calculations
placed Clavius somewhere in one of the transition regions of theeclipse, very close to the region of pure totality, and he describedthe “beaded” eclipse at its maximum as: “a certain narrow circle
was left on the Sun, surrounding the whole of the Moon on all
sides”. Despite the eclipse in Exmouth being of higher magnitude
than the one observed by Clavius, the absence of outer corona
and the presence of a bright rim of light all around the lunar limb
suggests we both had a similar view of the eclipse.
We hypothesise that the rim of light was due to the lowermost
layers of the inner corona which must have remained uncovered on
all sides of the lunar limb due to the near-unit magnitude of theeclipse. The light could not have been of photospheric origin as it
was continually visible throughout totality when there was no traceof photospheric continuum in the flash spectrum. During higher
magnitude eclipses, as it is often the case, only a small section ofthese layers can be seen at any one time during totality. We also
hypothesise that the brightness of the sky must have remained
unusually elevated, possibly because of the pristine sky conditions
as well as the narrowness of the umbral shadow path which would
have allowed a lot of diffuse light to flood the totality zone,
especially near its edges. That could explain why the outer corona
did not become visible.

It is important to stress that we are estimating the eclipse solar
radius Sꙩ (via Σꙩ ) as it appears in this formulation of the LDF and
we have no pretensions of measuring a physical parameter of
the Sun, such as the radius defined by some optical properties

JOURNAL FOR OCCULTATION ASTRONOMY I 2023- 4

19

Results”

The observed contact times are very likely affected by reaction
time, and the disappearance and reappearance of the photosphericcontinuum was rapid, but not instantaneous. The real contact
times might have occurred slightly earlier than measured, thus theestimated eclipse solar radius is probably slightly lower than that
implied by the observed C2 and slightly higher than that impliedby the observed C3. Therefore, we can say that the observation
supports the following estimate of the eclipse solar radius:
959.90” < Sꙩ < 960.02”

Result #1: Manual Contact Timings

This eclipse solar radius estimate is compatible with the one we
obtained by analysing a flash spectrum video [2] of the 2017 total
solar eclipse.

Result #2: Ambient Light Curves
The three loggers were deployed at the start of the eclipse
partial phase (before totality) and collected towards the end of theeclipse partial phase (after totality) between which they recorded
the level of ambient light. The loggers were placed horizontallyon the ground and left unattended. Figure 6 shows the signal
recorded by the data logger at Site 1. The photodiode signal
dropped by more than 4 orders of magnitude with respect to its
level outside the eclipse. The curve also includes the effect of theSun’s increasing altitude during the observation period, but theeffect of the eclipse is clearly seen.
The sky conditions were exceptionally favourable. At dawn somethin scattered clouds were visible towards the south affecting

Figure 5. Predicted contact times C2 and C3 for Site 1 as a functionof the eclipse solar radius Sꙩ. For Sꙩ = 960.28”, second and thirdcontacts occur simultaneously, totality lasts 0 s, and the northern
limit line passes through Site 1. Also indicated with dashed lines
are the manual contact time measurements which loosely support
959.90” < Sꙩ < 960.02”.

20

2023- 4 I JOURNAL FOR OCCULTATION ASTRONOMY

Figure 6. The ambient light curve recorded by the photodiode logger
located at Site 1. Note the greater than 4 orders of magnitude dropof the signal and the absence of any random dips in the signal, atestament to the pristine sky conditions present throughout theeclipse.

Journal for

Occultation Astronomy

about one third of the sky, but they quickly dissipated and by thetime the eclipse started, just after 10 am local time, the sky wasdeep blue from horizon to horizon and so remained throughout
the duration of the eclipse. The recorded light curves are therefore
very clean and do not show any random dips due to passing
clouds.
We focussed our analysis on the section of the light curve
encompassing totality, as shown in Figure 7. We note that theSun’s altitude hardly changed over the 1-minute interval
considered for this analysis. The light level during totality almost
reached the lowermost signal the logger could record. We canobserve some effects due to the discretisation introduced by the
ADC, where just before and just after totality the photodiodesignal was changing by increments smaller than the logger could
record.

to its minimum. To determine the error bars on the result wefollowed the empirical criterion described in [1] by looking for thevalues where the parabola reaches 10% more than its minimum
value. The results provide the following estimation of the eclipse
solar radius based on the data from the three photodiode loggers:

Site 1Site 2Site 3S = 960.25” ± 0.04”
S = 960.23” ± 0.04”
S = 960.25” ± 0.05”

Based on the methodology described in [1] the observed data
were fitted with synthetic light curves generated for various eclipse
solar radii, which involved finding the best linear transformation
matching the synthetic curve to the observed one. Figure 7 shows
the result of this procedure for the data collected at Site 1.
To determine which of the synthetic light curves best
reproduce the observed data we looked at the least-square errorof each of the fitting procedures, as shown in Figure 8. We built
an interpolating parabola through the least-square errors anddetermined which value of the eclipse solar radius corresponded

Figure 8: Least-square error of fitting the ambient light curve
collected by the photodiode logger at Site 1 with synthetic light
curves computed for various values of the eclipse solar radius Sꙩ.
The best fit is obtained for Sꙩ ≈ 960.25”.

Figure 7: Observed ambient light curve at Site 1 around the time of totality and three synthetic light curves for various
eclipse solar radii fitted to the photodiode signal.

JOURNAL FOR OCCULTATION ASTRONOMY I 2023- 4

21

Discussion
indi-rectly as diffuse light) is the only source of light. A filter was placedin front of the photodiode, and it is likely that almost all
chromospheric emissions were blocked. But there was that brightring of light around the rim of the Moon which was likely due toinner coronal light. The coronal light has a bright emission around
530 nm, which lies at the edge of the filter bandwidth. Hence,some of this light might have made it through the filter and been
captured by the loggers. Usually, we think about the inner corona
as far less intense than the photosphere but the intensity of the
Baily’s beads that appeared after C3 was rivalled, for 10-15 s, by thebrightness of the ring of light. This extra component might havethe effect of making the estimated eclipse solar radius slightly
larger than it should be because the synthetic curves are unable toaccount for the temporal dynamics of the light coming from thisintense rim of light (its contribution is likely not constant due to the
movement of the Moon).
Finally, we would like to highlight the fact that the eclipse
computations reproduce the timing of the observations remarkably
well. The UTC timing of the observed light curves is accurately
matched by the timing of the synthetic light curves. If the eclipse
computations did not accurately account for all the complexityof the lunar limb profile, of the movement of the centres of the
Sun and Moon, of the reference systems, etc, we'd likely see
timing mismatches, especially for locations so close to the umbral
shadow's path edge.

Conclusions
We estimated the eclipse solar radius Sꙩ to be in the range
959.90”-960.02” from manual contact timings obtained byobserving the eclipse flash spectrum and to be about 960.25” byanalysing ambient light curves collected with photodiode loggers.
The photodiode loggers were very easy to use but their analysis
raised several questions. We are aiming to use these loggers
again during TSE2024 to assess if the apparent peculiarities of
ATSE2023 might have affected the recorded data. However, ourmain effort will be to collect a time-stamped video of the eclipse
flash spectrum as we believe it to be a superior way of estimating
the eclipse solar radius.

References[1] Lamy, P., Prado, J.-Y., Floyd, O., Rocher, P., Faury, G., Koutchmy, S.,
A Novel Technique for Measuring the Solar Radius from Eclipse Light
Curves – Results for 2010, 2012, 2013, and 2015, Solar Physics, vol 290, pp
2617–2648 (2015)[2] Quaglia, L., Irwin, J., Emmanouilidis, K., Pessi, A., Estimation of the
Eclipse Solar Radius by Flash Spectrum Video Analysis, The AstrophysicalJournal Supplement Series, vol 256, no 2 (2021)[3] Hestroffer, D., Magnan, C., Wavelength dependency of the Solarlimb darkening, Astronomy and Astrophysics, vol 333, pp 338-342 (1998)[4] Stephenson, F.R., Jones, J.E., Morrison, L.V., The solar eclipse
observed by Clavius in A.D. 1567, Astronomy and Astrophysics, vol 322,
pp 347-351 (1997)

22

2023- 4 I JOURNAL FOR OCCULTATION ASTRONOMYBeyond Jupiter

The World of Distant Minor Planets

Since the downgrading of Pluto in 2006 by the IAU, the planet
Neptune marks the end of the zone of planets. Beyond Neptune,
the world of icy large and small bodies, with and without anatmosphere (called Trans-Neptunian Objects or TNOs) starts. This
zone between Jupiter and Neptune is also host to mysterious
objects, namely the Centaurs and the Neptune Trojans. All of thesegroups are summarised as ”distant minor planets”. Occultation
observers investigate these members of our solar system, without
ever using a spacecraft. The sheer number of these minor planets
is huge. As of 2023 October 11, the Minor Planet Center listed 1545
Centaurs and 3113 TNOs.
In the coming years, JOA wants to portray a member of this worldin every issue; needless to say not all of them will get an article
here. The table shows you where to find the objects presented
in former JOA issues. (KG)

20

No.

Name

AuthorLink to Issue

In thisIssue:

Logos and Zoe
kguhl@@astw.de2020. 

944

HidalgoOliver Klös

JOA 1 2019

2060

ChironMike Kretlow

JOA 2 2020

5145

PholusKonrad Guhl

JOA 2 2016

55576

5335

DamoclesOliver Klös

JOA 2 2023

60558

8405

Asbolus

Oliver Klös

JOA 3 2016

10370

Hylonome

Konrad Guhl

10199

Chariklo

15760

No. Name

AuthorLink to Issue

AmycusKonrad Guhl

JOA 1 2021

Echeclus

Oliver Klös

JOA 4 2017

90377

Sedna

Mike Kretlow

JOA 3 2020

JOA 3 2021

90482

Orcus

Konrad Guhl

JOA 3 2017

Mike Kretlow

JOA 1 2017120347

Salacia

Andrea Guhl

JOA 4 2016

AlbionNikolai Wünsche

JOA 4 2019134340

Pluto

Andre Knöfel

JOA 2 2019

15810

Awran

Konrad Guhl

JOA 4 2021

136108

HaumeaMike Kretlow

JOA 3-2019

20000

VarunaAndre Knöfel

JOA 2 2017

136199Eris

Andre Knöfel

JOA 1 2018

28728

Ixion

Nikolai Wünsche

JOA 2 2018136472

Makemake

Christoph Bittner

JOA 4 2018

32532

Thereus

Konrad Guhl

JOA 1 2023

174567

Varda

Christian Weber

JOA 2 2022

38628

Huya

Christian Weber

JOA 2-2021

208996

2003 AZ84

Sven Andersson

JOA 3 2022

47171

Lempo

Oliver Klös

JOA 4 2020

341520Mors-Somnus

Konrad Guhl

JOA 4 2022

50000

QuaoarMike Kretlow

JOA 1 2020

486958

ArrokothJulia Perła

JOA 3 2023

54598

BienorKonrad Guhl

JOA 3 2018-2004 XR190

Carles Schnabel

JOA 1 2022

2019-1 I JOURNAL FOR OCCULTATION ASTRONOMY

JOURNAL FOR OCCULTATION ASTRONOMY I 2023- 4

23

The Discovery
the stars and constellations.  She also set the vessels of the Sun The Name

Figure 1. The University of Hawaii 2.2-metre telescope is located near thesummit of Mauna Kea, on the Island of Hawaii. The 2.2-metre telescope was
the first large telescope constructed on Mauna Kea. It went into operationin 1970, and its early successes showed the excellent image quality andobserving conditions at the top of Mauna Kea.
(Source: https://about.ifa.hawaii.edu/facility/maunakea-telescopes/#uh88).

The Orbit

Figure 2. WFPC2 wide field camera for the Hubble Space Telescopein laboratory.
(Source: https://airandspace.si.edu/collection-media/NASMA20140124000cp01)

24

2023- 4 I JOURNAL FOR OCCULTATION ASTRONOMYJournal for

Occultation Astronomy

Figure 3. Orbit diagram and position of (58534) Logos and Zoe on 2023 November 15.
(Source: NASA/JPL Small-body database lookup, https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=58534)

Physical Characteristics.

Past Stellar Occultations

Figure 4. Orbit of Logos-Zoe in the sky plane [4].

JOURNAL FOR OCCULTATION ASTRONOMY I 2023- 4

25

.

Future Occultations

References[4] Noll, K. S. et al.: “Detection of Two Binary Trans-Neptunian Objects,
1997 CQ29 and 2000 CF105, with the Hubble Space Telescope”, The
Astronomical Journal, 124:6, 3424-3429 (2002)
https://arxiv.org/abs/astro-ph/0210593[5] Grundy, W. M. et al.: “Five new and three improved mutual orbits oftransneptunian binaries”, Icarus, 213:2, 678-692 (2011)https://arxiv.org/ftp/arxiv/papers/1103/1103.2751.pdf[6] http://www2.lowell.edu/users/grundy/tnbs/
58534_1997_CQ29_Logos.html[7] http://www.johnstonsarchive.net/astro/astmoons/am-58534.html[8] Barucci, M. A. et al.: “Compositional Surface Diversity in the TransNeptunian Objects”, The Astronomical Journal, 120:1, 496-500 (2000)
https://iopscience.iop.org/article/10.1086/301416/pdf

Useful Links
About objects like TNOs and Centaurs:
NASA/JPL Small-Body Database Lookup
https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/
Spacewatch, Lunar and Planetary Laboratory, University of Arizona
https://spacewatch.lpl.arizona.edu
Minor Planet Center
https://minorplanetcenter.net//

30 Years Ago – Last-Minute Updates of Predictions via E-mailFrom IOTA News by David W. Dunham, Occultation Newsletter Vol. 6, No. 1:

More communications from the past – The Occultation Newsletter Heritage Project
https://www.iota-es.de/on_heritage.html

262023- 4 I JOURNAL FOR OCCULTATION ASTRONOMYJournal for

Occultation Astronomy

Forming a New Occultation Observation Group in East Asia
Introduction
A new organisation for occultation observation in East
Asia : the International Occultation Timing Association - East
Asia (IOTA/EA), has just started with its inaugural meeting on
2023_August 27 (UT). It is a joint organisation of professional
and amateur astronomers. It consists of eight core members,
three regional directors, and ordinary members who are
officially registered after the inaugural meeting. The goal of
IOTA/EA is to promote occultation observation and to be apartner in planetary exploration and other research.

Background of the Formation of IOTA/EA
There have been many amateur astronomers in Japan withexperience in occultation observation. They have been
exchanging information and accumulating know-how on
occultation observation through the mailing list called JOIN
since 1995, and JOIN members are always making efforts toobtain better observation results and improve data analysis
techniques based on the activities of individual observers.
These activities are fully appreciated. However, in recent years,
in response to the rapidly increasing demand for occultation
observations and the increasing scientific research obtained
from occultation observations, to respond to these needs,organized occultation observations are necessary. Therefore,
we decided to create an organized group for occultation
observers. This is the IOTA/EA, which so far consists mainly ofJapanese occultation observers and includes observers fromneighbouring countries.
There is a particularly deep connection between planetary
exploration flyby missions and occultation observations. For
example, it was systematic occultation observations that led tothe discovery of the snowman-like shape of (486958) Arrokoth,
the flyby target of NASA's New Horizons mission. The Lucymission, which is the first space mission to flyby a populationof small bodies known as Trojans, includes occultation
observations as a fundamental part of the mission.
In Japan, prior to the formation of IOTA/EA, the Japanese
occultation community was asked by JAXA's DESTINY+ planetary mission team to determine the size and shape of asteroid(3200) Phaethon (the flyby target of DESTINY+) throughoccultation observations. This is because the DESTINY+ teamneeds to know the exact size of (3200)_Phaethon and create
a 3D shape model of the asteroid for mission planning. In
response to this request, a joint team of professional andamateur astronomers was formed and began the occultation
observation of (3200) Phaethon. It was in 2019. Since then,Figure 1. IOTA/EA logo selected from among 21 applications
from the general public.
the joint team carried out many observations, such as stellar
occultation by Triton on 2022 October 6, stellar occultationby (3200) Phaethon on 2022 October 21 (for DESTINY+),stellar occultation by (65803) Didymos from October toNovember_2022 (for DART), and stellar occultation by(98943)_2001_CC21 in January-March 2023 (for Hayabusa 2#).
Through the series of occultation observation experiences,many Japanese occultation observers are now able toobserve occultation events under difficult conditions, suchas the brightness of the occulted star fainter than 11-12 magor the duration of dimming as short as 0.1 sec. A series ofsuccessful systematic occultation observations and followedby significant contributions for planetary exploration missions
and scientific researches encouraged occultation observers.
Another reason that occultation observations have become
so popular in Japan is the development and popularisation of
CMOS cameras and GPS receivers. They are very important
tools to improve the efficiency of occultation observations
and data analysis to obtain accurate results. In addition,
there are external forces (1) Gaia's catalogue has improved
the positional accuracy of faint stars that were not previously
used to predict occultation observations, (2) the All Sky Survey
made the orbital accuracy of asteroids higher. These have led
to more accurate occultation predictions. Therefore, there isless chance for observers to be misled. All these circumstances
have encouraged the establishment of IOTA/EA.

JOURNAL FOR OCCULTATION ASTRONOMY I 2023- 4

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IOTA/EA's Projects
IOTA/EA will conduct the following five projects:• Holding annual meetings• Providing information, discussion, research, analysis, anddata storage on occultation and eclipse phenomena• Website and mailing list management• Cooperation and collaboration with relatedorganisations• Other activities necessary to achieve the purpose
The IOTA/EA provides information on occultation andeclipse phenomena observable from the East Asia region
through the website. This website is open to the public:
https://www.perc.it-chiba.ac.jp/iota-ea/wp/
Any member of IOTA/EA can discuss and exchange
information through the mailing list :ml@iota-ea.org

The IOTA/EA will prepare data storage to hold the raw
data, analysis result, etc. of each observed event (asteroid
occultation and lunar occultation) by the IOTA/EA members,
and make a data archive. The IOTA/EA cooperates with other
IOTA organisations to improve and disseminate the qualityof occultation observations and to derive scientific results.
The IOTA/EA conducts outreach and dissemination activities
to promote awareness of and support for IOTA/EA activities
and holds workshops to promote occultation observing andimprove observation/analysis techniques.
The lack of a common language in East Asia makes it
difficult to share information. Therefore, we have appointed
Regional Directors in the major regions. The role of theRegional Directors is to communicate with the observers in theregions where the Director resides and to provide informationfrom IOTA/EA to the local observers. And the Regional
Directors are also responsible for reporting the observation
results of the observers in their regions to IOTA/EA. In otherwords, the Regional Directors act as a liaison between IOTA/
EA and the observers in each region. IOTA/EA currently has
Regional Directors in Mainland China, Hong Kong and Taiwan,
and hopes to expand this observer network further.

Figure 2. A total of 44 people from Japan, Mainland China, Hong Kong,
Taiwan, and other IOTA organisations from the United States, Europe, andAustralia attended the inaugural meeting on 2023 August 27.

28

2023- 4 I JOURNAL FOR OCCULTATION ASTRONOMYJournal for

Occultation Astronomy

Everybody Can Join IOTA/EA
Those who wish to become a member of the IOTA/EA canjoin the group, even if they do not live in the East Asia.
Membership registration is available on the IOTA/EA website
https://www.perc.it-chiba.ac.jp/iota-ea/wp/about-iota-ea/
join-iotaea/.
IOTA/EA has two types of members: regular members andassociate members. The membership fee for regular members
is 1,500 yen per year, and there is no membership fee for
associate members. No membership fee will be charged in
Fiscal Year 2023 that is the special founding year of IOTA/EA.
All members will be registered as regular members. A request
for payment of membership fee will be sent from IOTA/EA
before the start of the FY2024. Those who have paid their fee
will continue as regular members in FY2024, and those whohave not paid will automatically become associate members.

Communication is basically in English. Members who are
not fluent in English can use automatic translation functions.
IOTA/EA organises workshops to improve the skills of local
occultation observers. The purpose of the workshop is totrain newcomers to occultation observation in each region,
so the workshop is basically conducted in the local language.
However, the observation manuals, observing tools, anddata analysis software distributed at the workshop will laterbe made available in English.
IOTA/EA will contribute to the dissemination and technicalimprovement of occultation observation in the Asian region.
We look forward to working with occultation observers
around the world. We hope that you will follow the activities
of IOTA/EA closely and support us.
Fumi Yoshida
Director, IOTA/EA
Public Relations and Training

Organisation of IOTA/EA (Alphabetical order by last name)
Chairpersons
Tsutomu Hayamizu [Saga Hoshizora Astronomy Center, Japan] (早水 勉)
Fumi Yoshida [University of Occupational and Environmental Health, Japan / Chiba Institute of Technology] (吉田 二美)
Secretary
Hayato Watanabe [JOIN (Japan Occultation Information Network)] (渡部 勇人)
Directors
Hiroshi Akitaya [Chiba Institute of Technology] (秋田谷 洋)
Tsutomu Hayamizu [Saga Hoshizora Astronomy Center, Japan] (早水 勉)
Kazuhisa Miyashita [JOIN (Japan Occultation Information Network)] (宮下 和久)
Hirotomo Noda [National Astronomical Observatory of Japan] (野田 寛大)
Mitsuru Sôma [National Astronomical Observatory of Japan] (相馬 充)
Hayato Watanabe [JOIN (Japan Occultation Information Network)] (渡部 勇人)
Fumi Yoshida [University of Occupational and Environmental Health, Japan / Chiba Institute of Technology] (吉田 二美)
Regional Directors
Chilong Lin [National Museum of Natural Science, Taiwan] (林 志隆)
Ye Yuan [Purple Mountain Observatory / Chinese Academy of Sciences] (袁烨)Wai-Chun Yue [Hong Kong Astronomical Society] (余 惠俊)
AuditorToshihiro Horaguchi [National Museum of Nature and Science,Tokyo] (洞口俊博)
Departments(1) Planetary and Asteroidal Occultations
Provide predictions of planetary and asteroidal occultations, receive and compile observation reports, and report to IOTA.
(2) Lunar Occultations
Provide predictions of lunar occultations, receive and compile observation reports, and report to IOTA.
(3) Website Management
Maintain and manage the Association's website.
(4) Storage of Observation DataStore and maintain observation data reported to the Association.
(5) Public Relations and Training
Publicise the Association's activities and conduct training and other activities necessary to achieve the Association's objectives.
(6) Local Branches
Organize and publicise activities in each region.
Each branch appoints one regional director to serve on the Board of Directors.

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The International Occultation Timing
Association’s 41st Annual Meeting,2023 July 15-16 via Zoom Online
Richard Nugent · IOTA · Dripping Springs, Texas · USA · RNugent@wt.net
ABSTRACT: IOTA’s 2023 Annual Meeting was held via Zoom online on 2022 July 15-16. 
Numerous presentations were made by members of the IOTA community worldwide. More than 60 attendees participated in the meeting.
The 41st annual meeting of the International Occultation Timing
Association was held on Saturday and Sunday 2023 July 15-16
via Zoom online. The meeting schedule and agenda are locatedon the IOTA web site [1].
Video recordings of the session are available on YouTube [2].

Saturday 15th July 2023 - Day 1
IOTA’s Vice President Roger Venable opened and welcomed
everyone to the meeting.

Business Meeting
Treasurer Joan Dunham presented IOTA’s financials andmembership status.
A full report of the business meeting is available [3].

Awardssupport digital cameras along with the current support for analog
cameras. I started programming the two applications seven years
based on a user error on my part while trying to use the currently
available recording software. I had just purchased an analog
camera used by IOTA members and found that it did not work on
my laptop computer. So ultimately I decided to write a program
to see if I could make it work, and that was the start of my two
applications.
The best part of writing the applications is that it has permitted
me to interface with many of the IOTA members, both for beta
testing the software and after the official release for reporting
issues. The membership has kept me intellectually stimulated,which is important to me because I have long since been retired
from programming for a company.
Regards,
Russ McCormick

Richard Nugent then presented IOTA’s Homer F. Daboll Award.
This award is given to recognize significant contributions to thefield of occultation science and to the work of IOTA. This year's
recipients are Russ McCormick and Tony George.
Russ McCormick is honoured for his development andmaintenance of IOTA Video Capture and its companion, IOTA
Video Playback. His attention to what observers wanted led tothe development of a software package that can be programmed
to capture data automatically from remote, unattended, small
Windows computers and tablets. This program is a mainstay ofmany observers’ data capture kit, a dependable and easy-to-use
facility. Also, it should be noted that he provides a detailed user
guide, a great benefit for those first using these programs. Russ
sent the following message upon his notification of the award:
Richard,Thanks for notifying me about the Homer Daboll Award.
I am honored and hope to perpetuate IOTA members trust in the
IOTA Capture and Playback software as we press on into the
future. I still have multiple years of work to do as I begin to30

2023- 4 I JOURNAL FOR OCCULTATION ASTRONOMY

Figure 1. Homer F. Daboll Award: Russ McCormickJournal for

Occultation Astronomy

eclipses [5].

honour.

Technical Sessions

Figure 2. Homer F. Daboll Award: Tony George

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Figure 3. Profiles recorded during occultations by (65803) Didymos and its satellite.
(Source: Occult V4, screenshot of N. Carlson's presentation)
webpage [6].

Figure 4.
Table of the 15 double star discoveries madewith asteroidal occultation observations in
2022. (Screenshot of D. Herald's presentation)32

2023- 4 I JOURNAL FOR OCCULTATION ASTRONOMY

discovering double stars. With several stations observing theseoccultations, the uncertainty in separation can approach <0.001". In
2022, 15 double stars were discovered by IOTA observers (Figure4). Discoveries are usually published in the Journal of Double Star
Observations [5] and will be added to the Washington Double
Star Catalog (WDS) [6] maintained at the USNO.

Journal for

Occultation Astronomy

Dave showed several individual asteroid profiles from wellobserved events. Occultation-derived sizes were compared tothose estimated by the satellites: NeoWise, AcuA and IRAS.
Occultation-derived sizes matched very well with the satellite
data within the uncertainties. He showed a few asteroid eventsin which a single chord was obviously off compared to thosemade by other observers. Dave postulated the source of thesemismatched chords was due to timing errors.

Steve Preston presented "Best/Brightest Asteroidal Events of
the Coming Year 2024". In earlier years before Gaia, there weren'tthat many bright star occultation events whose path could be
predicted accurately. Now with much improved predictions, there
are so many bright star easy to observe events. Thus it's beendifficult to choose the "best" events. Steve will have a webpage ofthese events posted soon. Some important NEA events for 2024
(Figures 5a-c):
 Aug 13: (65083) Didymos - a crucial event to refine its orbit.
 Nov 7: (3200) Phaethon, Europe Dec 22: (3200) Phaethon, USA

Figures 5a-c. Important NEA events for 2024.
(Screenshot of S. Preston's presentation, Occult V4.2023.6.18)
Steve then did a quick run through of the best worldwide
events over Europe, Australia, and Japan. Then he showed mapsof the best 2024 events over North America.

David Dunham presented "NEA Observations: Recent andUpcoming". The motivation for studying NEA's is for planetary
defence. Unlike the dinosaurs who had no way of knowing their
species would end from the Chicxulub event some 65 million
years ago, humans now rule and can predict when an NEA isapproaching the Earth. The first observed NEO occultation was
1975 January 24 of kappa Gem by the asteroid (433) Eros.
(3200)_Phaethon was the first asteroid discovered by the IRAS
spacecraft. The first occultation observationof the 6 km size
(3200) Phaethon was made 2019_July_29 over central California.
The chord profile of this 2019 event can be found one-half way
down the page at [7].
In 2021, occultation (plus radar) observations helped end therisk of the asteroid (99942) Apophis striking the Earth in 2029.
Other NEO occultations mentioned were of (65083) Didymos/
Dimorphos in 2022/2023, and (98943) 2001 CC21, an NEA flyby
target of Hayabusa2. David then showed 2 maps of NEA eventsin North America during 2023 to mag 12.0 and mag 13.0 for(3200)_Phaethon. He showed a list of 20 km sized objects that
could be hazardous events during the next 1,000 years. David thenshowed a map of the 2024 (65083) Didymos and (3200) Phaethon
events over North America (Figure 6). For more information see
the presentation [8].

JOURNAL FOR OCCULTATION ASTRONOMY I 2023- 4

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Figure 6. Best 2024 NEA occultations across North America. (D. Dunham, Occult V4.2023.7.9)

David Dunham then presented a talk about "Trojans, Centaurs,
KBO's and Main Belt Asteroids with Moons." He showed maps ofoccultations of distant objects for the rest of 2023 in N. America:
Titania, (19521) Chaos, (468861) 2013 LU28, (50000) Quaoar andWeywot, (54598) Bienor and Titan. Then he showed events of
Trojan asteroids (at Jupiter's L4 & L5 Lagrangian points) for the restof 2023 in N. America. SwRI has a page [9] showing Lucy mission
targets and their paths over N. America for 2023. David showed
more predictions by special main-belt asteroids for 2024 thatwill appear in the 2024 RASC Handbook. After showing several
more important occultation events, he closed with a map of thebest Lunar Grazing events for 2023 over N. America.

David Dunham next presented a talk about the upcoming"319 Leona Asteroid Occultation of Betelgeuse on December 12,
2023." Betelgeuse is the brightest star to date with the most
likelihood of having its occultation visible. The path of this event34

2023- 4 I JOURNAL FOR OCCULTATION ASTRONOMY

is visible from South Florida across the Atlantic Ocean throughsouthern Europe. Asteroid (319) Leona and Betelgeuse are nearly
the same size so the star will fade and have a possible 50%-80%
drop in brightness. This can be an unprecedented opportunity tohave an "annular type" eclipse of Betelgeuse. (319) Leona's longrotation period of 430 ± 2 hours complicates determining its sizeand shape.
David showed detailed maps of the path over South Florida
and Europe. On 2023 August 27, there is an occultation of(319)_Leona over N. America. Observers are encouraged to try
this one to help pin down (319) Leona's size. This Betelgeuse
event might be recorded by DSLRs using a smart phone timing
app. David encouraged this event to be observed by astronomy
clubs, college and advanced high school students near the path
to introduce them to occultation observations and their scientificvalue.

Journal for

Occultation AstronomyyDave Herald showed how using Google Earth in conjunction
with Occult V4 can create fence lines at any separation one
chooses. This can greatly simplify the spacing and assignment ofobservers both at fixed and mobile sites.
The Meeting formerly ended at 2:05 UT, July 16th.

Sunday 16th July 2022 - Day 2
Technical Sessions
Mitsuru Soma, Vice President for Grazing Occultation Services
started the meeting with a talk about "Lunar Grazing Observations."
M. Soma talked about important results from analyses ofobservations of lunar grazing occultations from 2021-2023. The
ZC_2061 graze on 2022 January 25 was observed by M. Ishida andH. Yamamura in Japan. Their observations clearly showed that thestar is double, and the relative positions of the star's components
were obtained from their observations (Figure 7). Actually the star's
duplicity had already been detected in 2014 by D. Gault and D.
Herald in Australia through their lunar occultation observations. It
turned out that the newly-obtained results about the relative
positions (separation and position angle) are significantly different
from those obtained in 2014. The ZC 1049 graze on 2021
September 2 was observed by J. Bourgeois and B. Goffin in
Belgium. They found that the star is a new double star. The ZC 709
graze on 2021 September 27 was observed at two stations by B.
Gährken in Italy and at one station by M. Turchenko in Russia. B.
Gährken also detected the star's companion at his first station. For
all of the three events mentioned here it was found that significant
corrections to the positions of the stars in Gaia DR3 were also
required (Figure 8). This demonstrates the importance ofobservations of lunar grazing occultations not only to find doublestars but also to analyse positional errors.

Figure 7. Light curve from Limovie [12] of the first disappearanceof the main and secondary component of ZC 2061, observed by
M. Ishida on 2022 January 25.

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Figure 8. Observations of the graze of ZC 2061 fitted to the lunar limb profile. The graze was observed by M. Ishida and H. Yamamura
on 2022 January 25 in Japan.

Fumi Yoshida discussed the new occultation observing
organisation, the International Occultation Timing Association East
Asia (IOTA/EA), in East Asia. This organisation will be officiallylaunched with its inaugural meeting on 2023 August 27. IOTA/EA isa joint organisation of professional and amateur astronomers. It
consists of core members, regional directors, and a large numberof members who are officially registered after the inaugural
meeting. The organisation of IOTA/EA was planned mainly by
Japanese members. The reason was a request from the DESTINY+
mission ((3200) Phaethon's flyby mission) for Japanese occultation
observers to perform an occultation observation of(3200)_Phaethon. The DESTINY+ mission needed to know theexact size of (3200) Phaethon and create a 3D shape model inorder to carry out the mission. A joint professional/amateur team
was organized to observe the occultation of (3200) Phaethon. The
unity of professionals and amateurs at this time was the motivation
for the creation of IOTA/EA.

Joint professional and amateur observing teams have been
formed several times and the following observations have beenmade: stellar occultation of Triton on 2022 October 6, stellar
occultation of (3200) Phaethon on 2022 October 21 (forDESTINY+), stellar occultation of (65083) Didymos in October November 2022 (for DART) and for the stellar occultation of(98943) 2001 CC21 in January - March (for Hayabusa2).

Some examples of international occultation observations inwhich Japanese observers have participated can be found in [13,14].

While JOIN is a group of individual observers, IOTA/EA will
disseminate and share the knowledge and experience accumulatedby JOIN and expand the number of occultation observers.

362023- 4 I JOURNAL FOR OCCULTATION ASTRONOMY

Now Japanese observers can observe occultation events withdurations as short as 0.1 seconds, the brightness of the occulted
object < 11-12 mag. There are many amateur astronomers inJapan who have made occultation observations. Since 1995, they
have been accumulating their expertise in occultation observation
by exchanging information through a mailing list called JOIN. In
JOIN, occultation observers collect observation results and data
analysis experience, and also study to improve observation andanalysis techniques.

Journal for

Occultation Astronomy

IOTA/EA also cooperates with neighbouring countries andaims to become an organisation that can collaborate on planetary
exploration missions and scientific observations by researchers.
IOTA/EA will do the following: Provide predictions of occultation
events observable in East Asia, submit observation reports to the
IOTA, then IAU and create data archives (light curves, AVI files,etc.). IOTA/EA will initiate observing campaigns for important
objects and conduct workshops to train beginners in observation/
analysis methods and tools, distribute observing manuals andpublish its activities on the web, so that the activities of IOTA/
EA are known to occultation observers around the world.
IOTA/EA will carry out occultation observations associated withplanetary exploration missions and scientific observations
proposed by researchers. In 2023, IOTA/EA's observing plan
includes (155140) 2005 UD, a candidate for the second DESTINY+
flyby target, and outer objects such as TNO and Trojans, with theaim of discovering rings and satellites. Since there is no common
language in East Asia, it is difficult to share information. Therefore,
they have appointed Regional Directors in major countries/regions.
The role of the Regional Directors is to communicate theinformation provided by IOTA/EA (written in English) to observers
in the countries/regions, in a language that local observers canunderstand, and to help communicate reports and questions fromobservers to IOTA/EA. IOTA/EA will help them to communicate
their reports and questions to IOTA/EA. In other words, theRegional Directors act as a liaison between IOTA/EA and theobservers in each region where the Director resides. IOTA/EA
currently has regional directors in mainland China, Hong Kong,
and Taiwan, and hoping to extend this observation network to ourfriends in the Southeast/Central Asia regions in the near future.
With the establishment of IOTA/EA, they would like to contributeto occultation observations in the East Asia region in close
cooperation with IOTA. The IOTA/EA webpage can be accessed at[15].

Joan Dunham presented this year's IOTA outreach at the annual
North East Astronomy Forum (NEAF) and other meetings. One
problem is how can IOTA find new observers and how effective
are our methods? Roxanne Kamin gave the IOTA presentation
on chasing tiny shadows. IOTA's NEAF booth received lots ofvisitors. Joan mentioned for potential new IOTA members thatin-person meetings can be expensive, meeting info may not be
disseminated and online meetings are time-consuming.
The Asteroid, Comets and Meteors conference was in Arizona
2023 June 18-23. There were multiple presentations including
recognizing occultation work by observers. An advantage of an
in-person meeting is the face to face interactions with scientists
from around the world. This conference does not make thepresentations available nor are there conference proceedings
published. The Gaia team highlighted the (4337) Arecibo satellite
discovery by the two occultations in May and June 2021.

At the conference, SwRI gave talks about the Lucy mission
targets. One target is the asteroid (15094) Polymele in which Tony
George's observation in March 2022 and light curve indicated a
possible moon. Marc Buie mentioned that he has a Sky andTelescope article for the September 2023 issue on occultations andthe Lucy mission targets. Joel Castro had a poster presentation
on "The Mexican Network for Stellar Occultations: A Professionaland Citizen Science Collaboration." And the Minor Planet Center(MPC) announced major upgrades to manage their data volumes.
Joan also mentioned they have started a monthly newsletter tocommunicate with their users as well as the general public.

Kevin Green spoke about a "Possible Adelheid moonlet andOther Upcoming Events." The (276) Adelheid occultation of
2022_August_31 yielded a possible moon, this observation Kevinmade (Figure 9). He showed the orientation of (276) Adelheid at
the time of the occultation. He showed an animation using theshape model of (276) Adelheid's 6.4 hour light curve - it was
fairly consistent with very little light variation. The estimates ofthe moon's probability of detection during an occultation was
400 to_1 - so he was quite lucky. With an estimated mass hepostulated a 1.8 day orbital period for such a moon around (276)
Adelheid. With 15 previous occultations, no light curves showed
evidence of a satellite. The shape models matched quite well withthe light curves with only minor disagreement.

Figure 9. The light curve from the occultation by asteroid(276)_Adelheid shows about 40 s after the reappearance of thestar a second event with a duration of 0.75 s. The occultation wasrecorded by Kevin Green on 2022 August 31.
Kevin showed upcoming maps of future (276) Adelheid events
in USA including 2023 September 23 (near where he lives) alongwith an estimated orientation of (276) Adelheid's rotational axis.
He is currently trying to recruit observers for this September 2023
event.

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Kevin Green 's next talk was about "Stellar Multiplicity &Asteroidal Occultations". The basic question is how many stars
are multiple systems? Kevin showed a graph showing it depends
on the star size. It is estimated that half of all stars belong tomultiple systems. A possible double star occultation will occur
2023 September 13 by the asteroid (256) Walpurga.

rve for reporting.

Dave Herald talked about "What Happens to an Observation
after Submission". Observations are first sent to the Regional
Coordinators (Australasia, Europe, USA, Japan, South America,
Unistellar) They consolidate all the observations, identify and try toresolve problems, fit an ellipse to observations and shape models,initiate double star analysis, asteroid satellite analysis andcoordinate with other coordinators when the event crosses otherregions. Following analysis, the events are sent to the Global
coordinator (Dave) in batches of 10 events. Dave then begins aquality assurance process: he closely reviews the analysis of shapemodel fitting, double star solutions, possible satellite discoveries. If
an observation appears to have a hidden problem, further analysis
and questions arise. The Unistellar telescopes observers are now
entering the field and these folks are now submitting observations.
Dave then showed a table from Occult showing asteroid diameterswith uncertainties from shape model fitting (DAMIT, ISAM).
For determining size and shape of asteroids, we need multiple
chords. Currently, most observations are single person/single
chord observations. Shape model investigators need occultation
chords to improve models. While shape models can give shape,
occultation observations give size. More studies are used in
combination with mass measurements from orbital perturbations
to derive densities of some asteroids.
After submitting observations to the MPC for years, in 2019 2023 they were put on hold. A serious review began detailing anerror model with assistance from JPL Horizons. MPC has beendeveloping a new reporting system using the standard Astrometry
Data Exchange Standard (ADES). A new MPC observatory code
has been assigned for occultations - 275. For some special
events, there is direct reporting to JPL Horizons with rapid orbit
updates as needed especially for predictions for future spacecraft
encounters. Dave showed an ADES sample page for submission ofdata. An example of the high credibility of our observations camewith 14 (65083) Didymos occultations through 2023 January_22
as compared to the DART OpNavs and radar measurements.
For double star discoveries, they will only be added to the
WDS by publication in a recognised journal such as the Journalof Double Star Observations (JDSO). Since the regional
coordinators don't have the time to write the papers, Davesuggested a standard pro-forma (template) paper which would
enable observers to easily prepare a paper for submission to
JDSO. Dave next discussed archiving with NASA's PDS system.
The current archive has been paused for several years. The next382023- 4 I JOURNAL FOR OCCULTATION ASTRONOMY

Figure 10. Prototype of ASTRID. The green LED for verification of
the timing is visible in the 1 1/4" nose piece.

Journal for

Occultation Astronomy

Bob Anderson continued with histalk about "A Set of Calibrated Video
Files for Evaluating Light Curve
Extractions." In this presentation, Bobannounced the public availability of asuite of test videos useful for testing
light curve extraction programs. The
videos are calibrated in the sense thatthe underlying light curves are known
and so can be compared with the‘answer’ produced by programs like
PyMovie. The videos are synthetic because they are the result of simulationsof the major factors present in reallife occultation recordings: shot noise;
scintillation noise; high and low altitude
turbulences; telescope/ optics; camera
characteristics. The talk included aslide for each of the underlying light
curves available in the test suite andconcluded with a link to the files [16].

Figure 11. Screenshot of the OccuWeather tool developed by Kai Getrost. The cloud maps
could be chosen from different providers.

Kai Getrost next discussed a Weather Forecaster for
Occultations: "OccuWeather - A Tool to Aid Occultation Weather
Planning." A typical occultation plan includes looking at several
online weather cloud forecast maps. The problem is these weather
maps don't have the occultation paths - one must mentally recall
the occultation path while looking at the cloud forecast map.
Kai created a website (currently under construction) for cloudforecasting [17]. Kai integrated the Google KML files to overlay theoccultation paths on the cloud maps. Both graphical forecasts andsatellite imagery are supported. The website currently has several
time-lapse cloud cover maps with the occultation paths overlaid
on them for North America, Australia/NZ and Europe (Figure 11).
Right now, Kai has to enter each occultation event map
manually which only takes a minute.
Kai's future work will include: Automatically set the forecast to the predicted event time
-The goal here is not having to "do the math" every time
one is checking the weather, e.g. not having to select"+72 hours" when checking 3 days before the event,then "+48 hours" when checking 2 days before, etc.
 Clicking on the map to get lat/long at any point Mobile/ tablet support
 Possibly integrate with Occult Watcher Cloud [18].

The meeting ended at 01:50 UT, July 17th.

References[1] Agenda on IOTA Meeting 2023 https://occultations.org/community/
meetingsconferences/na/2023-iota/[2] Playlist of recordings of IOTA Meeting 2023
https://www.youtube.com/playlist?list=PLPYvLiLF-6zsVP4tFsbsalAQWEaxYW-a[3] IOTA's Business Meeting 2023
https://www.poyntsource.com/Richard/IOTAMeeting2023.htm[4] https://www.asteroidoccultations.com/observations/Awards/IOTA
Awards.htm[5] Journal of Double Star Observations, http://www.jdso.org[6] Washington Double Star Catalog, http://www.astro.gsu.edu/wds/[7] http://www.poyntsource.com/Richard/IOTAMeeting2019.htm[8] https://occultations.org/publications/rasc/2023/ACM2023.htm[9] Lucy mission targets, SwRI,
https://lucy.swri.edu/mission/Targets.html[10] Glover, R., SharpCap, https://www.sharpcap.co.uk/[11] Herald, D., Occult V4 software,
http://lunar-occultations.com/iota/occult4.htm[12] Miyashita, K., Limovie software,
https://astro-limovie.info/limovie/limovie_en.html[13] https://academic.oup.com/pasj/article/75/1/153/6947807[14] https://www.esa.int/Enabling_Support/
Space_Engineering_Technology/
Shadow_hunters_capture_Didymos_asteroid_eclipsing_stars[15] IOTA/EA web page, https://www.perc.it-chiba.ac.jp/iota-ea/wp/[16] Anderson, B., PyMovie software,
https://occultations.org/observing/software/pymovie/[17] Getrost, K., Occuweather, https://occuweather.info/[18] Pavlov, H., Occult Watcher Cloud, https://cloud.occultwatcher.net/

JOURNAL FOR OCCULTATION ASTRONOMY I 2023- 4

39

Journal for

Occultation
Astronomy
IOTA’s Mission
The International Occultation Timing Association, Inc was established to encourage and facilitate theobservation of occultations and eclipses It provides predictions for grazing occultations of stars by the Moonand predictions for occultations of stars by asteroids and planets, information on observing equipment andtechniques, and reports to the members of observations made.
The Journal for Occultation Astronomy (JOA) is published on behalf of IOTA, IOTA/ES and RASNZ and for theworldwide occultation astronomy community.

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Imprint
Publisher: International Occultation Timing Association/European Section e.V.
Am Brombeerhag 13, D-30459 Hannover, Germany
Responsible in Terms of the German Press Law (V.i.S.d.P.): Konrad Guhl
Editorial Board: Wolfgang Beisker, Oliver Klös, Alexander Pratt, Carles Schnabel, Christian Weber
Additional Reviewers: Richard Miles
Contact: joa@iota-es.de
Layout Artist: Oliver Klös
Webmaster: Wolfgang Beisker
JOA Is Funded by Membership Fees (Year):
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IOTA/ES: €20.00
RASNZ: NZ$35.00
Publication Dates: 4 times a year

Submission Deadline for JOA 2024-1: November 15

IOTA on theWorld WideWeb
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www.occultations.org
www.iota-es.dewww.occultations.org.nz
These sites contain information about the organisation known as IOTA and provide information
about joining.
The main page of occultations.org provides links
to IOTA’s major technical sites, as well as to themajor IOTA sections, including those in Europe,
East Asia, Middle East, Australia/New Zealand,
and South America.
The technical sites hold definitions and information
about all issues of occultation methods. It contains
also results for all different phenomena. Occultations by the Moon, by planets, asteroids and TNOs
are presented. Solar eclipses as a special kind of
occultation can be found there as well results ofother timely phenomena such as mutual events ofsatellites and lunar meteor impact flashes.
IOTA and IOTA/ES have an on-line archive of allissues of Occultation Newsletter, IOTA’S predecessor to JOA.

Journal for Occultation Astronomy(ISSN 0737-6766) is published quarterly in the USA
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