Vol. 6 No. 3 July 1, 2010

Journal of Double Star Observations

Page 176

Lunar Occultation Observations of Known
Double Stars – Report #1
Brian Loader, Darfield, New Zealand (BL)Royal Astronomical Society of New Zealand (RASNZ)International Occultation Timing Association
Y. Asada, Otsu, Kyoto, Japan (YA)
D. Breit, Morgan Hill, California, USA (DB)J. Bradshaw, Yugar, Queensland, Australia (JB)
D. Gault, Hawkesbury Heights, NSW, Australia (DG)
D. Herald, Kambah, Canberra, Australia (DH)E. Iverson, Lufkin, Texas, USA (EI)
M. Ishida, Matusaka, Mie, Japan (MI)H. Karasaki, Nerima, Tokyo, Japan (HK)M. Kashiwagura, Oe, Yamagata, Japan (MK)K. Miyashita, Azumino, Nagano, Japan (KM)
S. Messner, Minneaplois, Minnesota, USA (SM)T. Oono, Kurashiki, Okayama, Japan (TO)S. Russell, North Parramatta, Sydney, NSW, Australia (SR)G. Smith, Black Town, Sydney, NSW, Australia (GS)J. Talbot, Waikanae, New Zealand (JT)
Email: palbrl@clear.net.nz

Abstract: Reports are presented of lunar occultations of close double stars observed using
video including cases where a determination of the position angle and separation of the paircan be made and other cases where no duplicity has been observed.

This report is the first of a continuing series ofdouble star measurements made during lunar occultations. The observations are contributed from observers around the world who observe lunar occultations. Unless noted otherwise, the observations weremade using video at 30 fps (observers located in
North America and Japan) or 25 fps (observers located in Europe and Australasia). Loader, in New
Zealand, normally uses a 30 fps video.
In general, at the lunar occultation of a doublestar, the light from the star will disappear or reappear in stages, resulting in a stepped light curve ofthe event. We present the results obtained from thetiming of such events of close double stars, in general
limited to those with separations less than 2 arcseconds. When the occultation of a double star is
timed from two or more well spread locations an accurate determination of the PA and separation of thepair can be made. Results for a few such events arepresented in Table 1. When only one observation ismade of a double star occultation a complete solution
is not possible, but a vector (minimum) separation of
the pair may be determined. Results of such eventsare presented in Table 2.
The method of analysis of such occultation observations is described by Herald (2009). The occulta-

Vol. 6 No. 3 July 1, 2010

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Journal of Double Star Observations

Lunar Occultation Observations of Known Double Stars – Report #1
tions are observed using unfiltered video cameras. As
The companion of the double stars listed in Table 2
indicated by Herald, the unfiltered video cameras have was observed at a single position angle, allowing thea spectral response somewhere between the V and R determination of a vector separation and magnitude
magnitude bands.
difference.
Observations of occultations of reported double
In Table 3, the companion of the stars listed in thestars when no evidence of a double nature is observed WDS was not observed. Either the vector separation
are presented in Tables 3 and 4. The apparent lack of was too small, or the magnitude difference too large for
duplicity may be due to a number of factors as indi- the circumstances of the event.
cated in the headings of the tables. Instances are limTable 4 contains stars with an entry in the Interited to those for which there are at least two observa- ferometric Catalog but for which no companion wasobserved. Possible explanations are:tions with no duplicity observed.
i. the vector separation was too small;In the tables observers are indicated by a two letii. the magnitude difference too large for the circumter code corresponding to their initials codes. Names
stances of the event;are listed at the head of this paper. WDS refers to theiii.
the purported companion does not exist.
Washington Double Star Catalog and IF to the Interferometric Catalog, both published by United States Naval Observatory, Washington. XZ refers to the XZ80 References
catalog originally put out by the USNO. It includes allstars to magnitude 12.5 within 6°40’ of the ecliptic, Herald, D. “ SAO97883 – a new double star”, JDSO,Vol 5, No 4, 2009that is all stars which can be occulted by the moon.
Occultations of the double stars listed in Table 1
were observed at two or more position angles on thesame night, allowing a determination of the separationand position angle.

Table 1: PA and separation measured
PA+/-Sep+/-Mag.
diff

DateObservers

07227+2205

304

4

1.84

0.17

1.4

2009.851

HK, MI, MK

10135607260+2205

165

4

1.38

0.15

0.8

2009.851

HK, MK

16040

10426+0335

241

4

0.41

0.08

1.3

2009.413

DB, EI, SM

0.016+0.006-0.002

2.5

2009.214

DG, BLWDS nameXZ

HO345AB

10979

AG140A

2768

RADec

78

25788

18448-2501

8+21-35FIN 327

26957

19253-2431

275

170.095

0.005

1.5

2008.693

DG,DH,GS,JB

CHR 184Aa,Ab

28441

20273-1813

50

70.0710.015

2.6

2009.668

DH,BL

SHJ 323AB

28475

20289-1749

214.8

1.2

1.44

0.02

1.7

2009.668

DH,BL

HDS305429697

21274-1335

357

60.1130.013

1.5

2009.747

EI,DBCHR

Vol. 6 No. 3 July 1, 2010

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Journal of Double Star Observations

Lunar Occultation Observations of Known Double Stars – Report #1
Table 2: Vector separation measuredVectorAngle

Vector
Sepn.

Mag.
DiffDateObserver

04536+2522

265.910

0.34”

1.75

2009.845

SM

7200

05365+2556

334.873

0.06”

0.98

2009.856

MK

COU 9149119

06283+2441

280.129

0.20”

0.86

2009.700SMHDS 9109439

06375+2435

273.696

0.45”

2.56

2009.867

SMHO

247

11655

07461+2107

274.531

0.49”

0.51

2009.770

MICOU 77313520

08539+1958

79.7210.135”

0.52

2008.134

DG

HDS132313821

09062+1552

323.032

0.17”

2.55

2009.407

DHHO

253

14778

09478+1004

348.300

0.77”

2.3

2009.410

EI

BU

932AB

19503

13347-1313

133.3970.11”1.6

2007.179BLHDS2008

20149

14171-1835

359.7640.014”

3.5

2009.199

BL

BU

125AB

23196

17122-2703

73.543

1.81”

1.7

2008.611

DHI

1031

26024

18531-2745

25.709

0.24”

0.97

2005.774

DG

WDS name

XZ

RACHR 127AB

6268

CHR 203

Dec

Table 3: Companion not observed (definite double star)
WDS name

XZ

RA

Dec

CHR 124Aa,Ab4889

03470+2431

SMK

1Aa,Ab8068

06010+2734

CHR 170Aa,Ab10181

06588+2605

MCA28

10203

06595+2555

TDS973940376

16026-2452

FOX 256
See note

29337

21084-1454

CHR 11631135

22583-0224

Vector
angle
222°
118°
35°
51°
57°
52°
89°
88°
86°
82°
135°
113°
114°
194°
207°
352°

Resolution Limiting
limit
Mag. diff
0.034”--0.022”--0.015”
20.022”30.023”30.020”30.031”30.030”30.031”2.5
0.031”
2.70.027”
0.70.016”
2.70.015”
30.023”30.025”2.70.012”
2.5

Date

Observer2007.672
2009.095
2009.174
2009.174
2009.177
2009.177
2009.177
2009.177
2009.654
2009.654
2009.654
2009.895
2009.895
2009.602
2009.602
2009.826

SMSM
DG
DHDHDGDHDGDHSRJTKMMIDGDBYA[The ‘Resolution limit’ is set at no less than two frame intervals [0.080s (PAL) or 0.067s(NTSC)] times the vector rate of motion.]

Table note: The WDS shows FOX 256 as a pair with a separation 10.4” measured in 1908. The IF has a single entry for
FOX256 from 1991 showing any separation as < 0.1. The light curves from occultation observations show no second
star with a vector separation less than ca 1.3”.

Vol. 6 No. 3 July 1, 2010

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Journal of Double Star Observations

Lunar Occultation Observations of Known Double Stars – Report #1

Table 4: Companion not observed (possible double star)Star nameXZRADec

BD+06 43482

00257+0741

Iot Ari

2721

01574+1749

BD+214151

03107+2154

416

Mel 22 541

4829

03452+2450

Pleia H256

4831

03453+2428

Mel 22 697

4840

03456+2428

OCC 1934863

03459+2433

Eta Tau4911

03475+2406

BD+25 678

5382

04087+2553

OCC 1156938

05263+2836

BD+15 1977

13824

09064+1516

CP-25 6547

25420

18317-2541

HR 7039

25814

18457-2659Vector
angle

Resolution
limit

265°
95°
165°
185°
290°
73°
200°
309°
237°
88°
101°
220°
245°
211°
238°
217°
105°
227°
41°
127°
67°
201°
142°
320°
68°
306°
312°
118°
7°
324°
271°

0.029”
0.022”
0.008”
0.020”
0.017”
0.029”
0.018”
0.012”
0.030”
0.025”
0.014”
0.022”
0.037”
0.035”
0.026”
0.026”
0.021”
0.026”
0.021”
0.015”
0.026”
0.020”
0.017”
0.017”
0.018”
0.033”
0.033”
0.028”
0.012”
0.021”
0.031”

Limiting
Mag. diff

2.5
2.51.8
2.8
2.5
4
2.7
--23
3
--3.5
--3----333
33
2.7
2.5
3.5
2.5
2.7
2.5
2
-----

Date

Observer2008.709
2008.860

DH
BL
DH
DG
BL
TO
HK
BL
DG
DH
DH
BL
SM
BL
DG
BL
SM
SM
YA
DG
SM
DG
DG
BL
SM
DH
DG
DG
DB
BL
BL

2008.789
2009.461
2005.648
2006.921
2009.840
2005.725
2009.692
2009.917
2010.066
2005.725
2007.672
2005.725
2007.672
2005.725
2009.095
2009.618
2009.917
2006.026
2007.075
2009.618
2008.200
2008.723
2009.330
2009.930
2009.930
2008.915
2009.662
2004.350
2007.420[The ‘Resolution limit’ is set at no less than two frame intervals [0.080s (PAL) or 0.067s (NTSC)] times thevector rate of motion.]