WGN, the Journal of the IMO 37:2 (2009)

55

Ongoing Meteor WorkA meteor shower catalog based on video observations in 2007–2008
SonotaCo 1
A new meteor shower catalog was established from two years of continuous video observations based on almost
240,000 single-station observations by more than 100 video cameras operated at 25 stations in Japan. 39 208
meteor orbits were computed from them as qualified multi-station observations. From this sample, 38 meteor
showers were obtained as the result of applying a uniformized method of clustering in the four-dimensional
space of appearance in Solar longitude, radiant position, and geocentric velocity. The full set of showers in the
new catalog covered 37% of all meteors. No other concentration was confirmed from the remaining 63%. The
catalog is the first one based on long term, wide area, multi-station video observations, and shows the recent real
activity for all major meteor showers that are optically observable from northern hemisphere. Eleven showers
have been added to the list of meteor showers of the IAU Meteor Data Center (MDC).
Received 2009 January 29

1

Introduction

Automated multi-station video meteor observations
present a very good detection ability, fair accuracy oforbit computation, and the capability for long term continuous observations necessary to creating a shower catalog.
UFOCapture (SonotaCo, 2005) is a motion detection software which allows video recording from a
few seconds before the trigger. Written by SonotaCoin 2003, it has been used by scientific observers chronicling rare events such as meteors or TLEs (transient
luminous events caused by lightning discharge). By theend of 2006, the meteor measurement software UFOAnalyzerV2 (SonotaCo, 2007), and the orbit computation software UFOOrbitV2 (SonotaCo, 2007) had
been published, and the environment for multi-station
meteor observation had been established. Results of thesystem have already been used for the detection of theτ -Ursae Majorids (Uehara, et al., 2006; now October
Ursae Majorids) and the analysis of meteor altitudes(Molau & SonotaCo, 2008).
Having started as an online user forum for UFOCapture, SonotaCo Network has been working since2004. The members of the network are amateur astronomers, staffs of public observatories, and a few professional researchers. The network itself had grown tomore than 30 stations by 2007. These stations are observing the night sky above Japan every night, evenwhen it is raining.
In this paper, we describe a set of meteor showers
which are a result of two years of observations by the
SonotaCo Network.

2

Outline of observation

For this study we used the SonotaCo Network’s published observational results for the period 2007 January 1 to 2009 January 1 (731 nights). This data was
1 3-20-4 Daita Setagaya-ku, Tokyo, Japan
E-Mail: sonotaco@yahoo.co.jp

IMO bibcode WGN-372-sonotaco-catalog
NASA-ADS bibcode 2009JIMO...37...55S

Figure 1 – Observation area and the stations.

compiled by 25 stations using more than 100 cameras.
The totals are listed in Table 1, and the contributing
stations are listed in Table 2. Figure 1 shows the distribution of the observed trajectories. Many stations use
multiple cameras with standard lenses to inprove theaccuracy and to cover larger area. The typical equipment is as follows: Camera: Hi-sensitivity monochrome CCD video
camera, WATEC-100N or WATEC-902H2U.
 Lens: CS-mount lens, f /0.8, f = 3.8 − 12 mm(FOV: 90 – 30◦ ).
 Video format: 720 × 480 or 640 × 480 AVI digitized from analog NTSC signal (29.97fps, interlaced).
 Software: UFOCaptureV2, UFOAnalyzerV2,
UFOOrbitV2.

56

WGN, the Journal of the IMO 37:2 (2009)

Table 1 – Totals of the observations in 2007–2008.

Number of single-station meteors:
Number of qualified single-station meteors:
Number of single-station observations
composing simultaneous observations:
Number of meteors qualified for
multi-station observation:
Average number of simultaneous observations per meteor:
Average number of qualified meteors per night:
Number of nights with > 100 qualified meteors:
Number of nights with no meteor observed:
Top 6 nights which had most meteors (UT)

293 702244 247
114 026
39 208 (see Figure 2)
2.93 camera/meteor
53.6 meteors/night
120 nights / 2 years
133 nights / 2 years
2007/12/14 (1051 meteors)
2007/08/12 (845 meteors)
2007/12/13 (796 meteors)
2007/08/13 (700 meteors)
2007/10/20 (655 meteors)
2008/12/14 (603 meteors)

Table 2 – Number of single-station observations and the observers. (The location ID includes the prefecture name inJapan.)

Location ID

Observations

Akita1
Chiba2
Fukuoka1
Fukushima1
Ishikawa1
Ishikawa2
Kanagawa1
Miyazaki1
Okayama1
Okayama4
Nagano1
Niigata1
Niigata2
Osaka01
Osaka03
Saitama1
Saitama2
Sizuoka3
Tokyo1
Tokyo2
Tokyo4
Tokyo5
Tokyo6
Toyama1
Toyama2
Others

3304
18843
720
687
4169
13078
19744
11457
4749
297
56576
138
19113
17063
12011
37531
604
99
34232
536
6338
20914
7281
4460
204
52

Observer
Izumi
Ada
Shigetaka Shiraishi
Hiromichi Horigane
Hideaki Muroishi
Hiroshi Yamakawa
Hiroyuki Inoue
Kouji Maeda
Junichi Yokomichi
Junichi Yokomichi
T. Masuzawa
PURU
Toshio Kamimura
Satoshi Uehara
Masayoshi Ueda
Takashi Sekiguchi
NOMOTO Satoko
SonotaCo
SonotaCo
Koji Ito
Hiroshi Yamakawa
Junichi Nakai
Naoya Saito
Toyama Astronomical Observatory
T. Komai–WGN, the Journal of the IMO 37:2 (2009)57

Figure 2 – Radiant of 39 208 meteors observed over two years, in a sinusoidal projection with x the right ascension α andy the declination δ (J2000.0). The original graph with the colour coded geocentric velocity is printed on the outer backcover.

3

 Records that have big errors caused by an explosion, asymmetrical brightness, or backgroundnoise.

Observation accuracy

The typical accuracy of single-station observation measurement is 0 ◦. 03 for the direction and 0.5 s for the absolute timing. This level of accuracy is achieved from
UFOAnalyzerV2 plate adjustment using fixed stars
and time synchronization obtained from Network Time
Protocol on the Internet. The time resolution is 0.017 s,
and it is very accurate for timing of NTSC video. Thisaccuracy can be used as basic measurement accuracy
for most of the meteors which show a narrow trajectoryand no burst or explosion.
The accuracy of the radiant position and the velocity depend on the geometric conditions of simultaneous observations, such as distance from station to themeteor or the cross angle of the observed planes. Although UFOOrbitV2 improves the accuracy by calculating all (more than two) simultaneous observations
by the least square method (unified radiant mode), theeffectiveness of this method also depends on the numberof simultaneous observations and their geometric situations. Therefore, the accuracy is different for each meteor. In this study, the lowest quality check of UFOOrbitV2 (mode Q1) was used for all data. It checks theintersection angle, duration time, height, velocity, andmatching of the trajectory. It rejects results which haveobvious large errors. As a statistical result, the radiantof compact showers, such as the Quadrantids, show aconcentration within a radius of a 3◦ circle, and 20% deviation of the velocity if data from one night are used.
The commixture of non-meteoric objects such as air
planes, satellites, or cosmic ray noise was negligible, because all single-station observations have been checked
manually by the observer and UFOOrbitV2 checkedit again. But because the post-process was fully automated, the data set possibly includes a small number ofthe following cases: Mis-combined data from multiple meteors whichhappened almost simultaneously, close to eachother, and along a very similar vector.
 Mis-combined data caused by time adjustment
failure.

4

Statistical bias of the data set

The analysis involves a number of different biases which
are discussed here.
Magnitude: Figure 3 shows the distribution ofmagnitudes. The average visual magnitude was 0.84
for single-station observations, and 0.20 for simultaneous observations. The average absolute magnitude was

Figure 3 – Distribution of meteor magnitudes. Single v-mag
is the visual magnitude of single-station observations, multiv-mag the visual magnitude of simultaneous observations,and multi a-mag absolute magnitude of qualified meteors.

58

WGN, the Journal of the IMO 37:2 (2009)

Figure 4 – Radiant areas of 38 meteor showers obtained from the clustering.

−0.87. Meteors fainter than absolute magnitude 2.0 arevery rare in the set.
Length: meteors which had less than 1◦ trajectory
length were rejected.
Geographical condition: all observations weremade in the latitude range between 32◦ and 40◦ N.
Therefore, many of the southern hemisphere radiants
are out of range.
Weather: the dependency on the weather over Japan in 2007 and 2008 was not small. The effect ofclouds, reduced transparency, or Moon light could not
be omitted even by combining data collected over two
years.

5

Clustering method

The purpose of clustering is to determine the set of theminimum number of meteor showers which covers all
obvious concentrations and does not include too many
sporadic meteors. Correcting for clustering also meansthat we obtain a smooth distribution of sporadic meteors.
This clustering was done in a four-dimensional space.
The axes are the time of the meteor appearance in Solar ecliptic longitude (λ⊙ ), the radiant’s right ascension(αp ) and declination (δp ), and the geocentric velocity(Vg ). The radiant positions αp , δp and the velocity Vg
are corrected for the effect of zenith attraction due tothe Earth’s gravity. As is well known, the observed
radiant position and observed velocity varies with theradiant elevation angle in the sky, while αp , δp and Vg
do not depend on the time of night.
In this study, one shower is expressed by 10 parameters as summarized in Table 3. The clustering involved
the following steps.

the center of the largest concentration in the set
and select it as the reference. (A dominant orbitof a known shower can be used as the reference
for the confirmation of shower’s existence.)
3. Clustering: select meteors which are close to thereference in the four-dimensional space from theset. Consider the radiant drift if it has alreadybeen computed. Then, the ranges of λ⊙ , R and∆V are tuned, depending on the characteristicsof the shower, to cover the whole concentrationand not to include too many surrounding sporadic
meteors.
4. Reference update: compute the shower parameters from the selected meteors, and update thereference as the center of selected meteors.
5. Iteration: repeat steps 3 and 4 until the association of the selected meteors does not change, oran association to another shower occurs.
6. Set update: once a cluster is found, its parameters
are recorded and the clustered meteors are deleted
from the set. Then the procedure is repeated fromstep 2 until all concentration disappears.

After this process, parameters of other known showers were checked to find out whether there was any concentration among the remaining meteors. If the concentration was confirmed and compared with the sporadic
meteors surrounding it, then it was added to the catalog even if the number of observations was small The
checked known radiants were those in the established
1. Initialization: combine a meteor data set from all
IAU list (IAU, 2008) which contains 56 showers, andobservations.
the UFOAnalyzerV2 current stream list (145 show2. Reference making: select one meteor which is near ers).

IAU Code

Name

λ⊙ 1
[◦ ]

λ⊙ 2
[◦ ]

λ⊙ p
[◦ ]

Date
(2008)αp[◦ ]334 DAD
331 AHY
018 AND
343 HVI
342 BPI
001 CAP
020 COM
335 XVI
221 DSX
191 ERI
145 ELY
031 ETA
344 JUG
004 GEM
016 HYD
012 KCG336 KDR
013 LEO
022 LMI
006 LYR
019 MON
337 NUE
250 NOO
017 NTA
281 OCT
338 OER
008 ORI
183 PAU
007 PER
339 PSU
010 QUA208 SPE
005 SDA
002 STA
340 TPY
333 OCU
015 URS341 XUM

December α-Draconids
α-Hydrids
Andromedids
h-Virginids
August β-Piscids
α-Capricornids
December Comae Berenicids
December χ-Virginids
Daytime Sexantids
η-Eridanids
η-Lyrids
η-Aquariids
July γ-Draconids
Geminids
σ-Hydrids
κ-Cygnids
December κ-Draconids
Leonids
Leonis Minorids
April Lyrids
December Monocerotids
ν-Eridanids
Nov. Orionids
Northern Taurids
October Camelopardalids
o-Eridanids
Orionids
Piscis Austrinids
Perseids
ψ-Ursae Majorids
Quadrantids
September-Perseids
Southern δ-Aquariids
Southern Taurids
θ-Pyxids
October Ursae Majorids
Ursids
ξ-Ursae Majorids

236.4
266.3
212.6
27.8
128.8
114.3
244.0
246.1
187.8
124.1
42.5
34.7
121.8
245.6
227.9
123.7
239.7
220.9
203.7
24.3
245.6
156.8
228.7
202.9
188.8
227.9
178.9
124.0
119.0
240.0
276.4
154.8
118.0
178.0
239.9
194.6
257.0
296.8

278.3
290.8
241.9
43.6
151.2
138.4
311.2
266.4
190.9
147.4
54.2
68.7
128.8
279.4
280.6
155.5
259.7
247.1
220.9
41.6
269.9
174.5
260.2
258.0
199.9
245.0
234.0
140.6
160.5
265.1
291.1
181.2
145.4
275.3
256.2
214.6
282.7
306.3

256.5
279.0
228.6
39.0
140.0
126.1
265.7
256.7
189.2
137.6
49.8
46.3
125.3
261.4
252.9
140.7
250.2
235.4
208.9
32.5
257.6
167.9
249.2
234.4
197.1
234.7
207.9
133.2
139.2
252.9
283.1
167.1
129.7
219.7
249.4
204.7
265.5
300.6

12/08
12/30
11/10
04/29
08/12
07/28
12/17
12/08
10/02
08/09
05/10
05/05
07/28
12/13
12/04
08/13
12/02
11/17
10/22
04/22
12/09
09/10
12/01
11/16
10/10
11/16
10/21
08/05
08/11
12/04
01/04
09/09
08/01
11/01
12/01
10/17
12/17
01/21

207.9
124.9
22.5
204.2
346.4
305.7
159.7
186.8
156.3
44.5
291.7
338.3
280.1
112.8
123.2
285.0
186.0
153.9
158.8
272.6
100.1
68.7
92.6
62.0
163.3
60.7
95.5
352.8
47.2
167.8
230.0
47.3
341.9
50.1
139.0
147.6
215.1
169.0

δp .
[◦ ].

∆α
[◦ ]

60.6
0.40
−7.7
0.45
29.7
0.12
−11.6
0.11
1.4
0.74
−9.4
0.50
31.6
0.79
−7.9
0.20
−2.9 −0.76
−11.7
0.49
43.8
0.20
−0.8
0.62
51.1
1.17
32.3
0.90
3.0
0.49
50.1
0.45
70.1
0.05
21.9
0.56
37.1
0.44
33.2
0.82
8.2
0.52
1.1
0.14
15.4
0.53
24.0
0.65
76.7 −0.93
−1.5
0.65
15.5
0.61
−20.4
0.27
57.7
1.17
44.5
0.20
49.0
0.15
39.3
0.77
−16.2
0.62
13.4
0.73
−25.5
0.43
64.0
0.13
76.2
0.94
33.0 −0.13

∆δ
[◦ ]

Vg
[km/s]

R[◦ ]∆V[km/s]

Number of
meteors

−0.14
−0.10
0.30
−0.27
0.22
0.26
−0.32
−0.14
−0.86
0.03
0.02
0.29
1.45
−0.19
−0.12
0.45
−0.09
−0.39
−0.08
−0.29
−0.11
−0.13
−0.04
0.12
−0.13
−0.03
0.01
−0.03
0.19
−0.01
0.17
0.06
0.26
0.16
0.04
0.09
0.04
0.01

41.0
44.2
17.0
18.7
38.3
22.4
63.0
67.8
31.2
64.0
44.3
65.4
27.4
33.5
59.0
21.9
43.4
70.0
61.9
46.7
41.2
65.9
42.0
26.7
45.3
26.9
66.2
42.8
58.7
60.7
40.0
63.9
39.4
27.2
60.1
54.4
33.2
40.2

9.0
5.0
5.0
3.0
6.0
6.0
6.0
3.0
3.0
6.0
4.0
5.0
4.0
7.0
7.0
10
4.0
4.0
4.0
5.0
3.0
3.0
4.0
5.5
5.0
5.0
4.0
4.0
5.0
3.0
5.0
5.0
4.0
6.0
3.0
4.0
5.0
5.0

4.0
3.0
5.0
3.0
4.0
3.0
4.0
7.0
3.0
6.0
3.0
5.0
3.0
12.0
5.0
5.0
3.0
7.0
6.0
5.0
3.0
3.0
5.0
4.0
5.0
4.0
8.0
3.0
20.0
3.0
6.0
4.0
4.0
5.0
3.0
3.0
5.0
3.0

145
38
18
16
71
122
652
31
4
86
14
220
22
2510
699
213
61
713
39
73
161
29
210
475
10
26
2733
10
3524
33
243
109
324
707
23
15
28
12

SN2006–
J1 aHyJ1 tPs
–J1 bPsJ1 CapJ1 Com
–J3 Sex–J1 eLyJ1 etA–
J1 GemJ1 Hyd
J1 kCg,gDr
J1 aDr
J1 LeoJ1 LmiJ1 LyrJ1 Mon–J1 nOrJ1 nTa–J1 bErJ1 OriJ1 oAqJ1 Per–J1 QuaJ1 gAnJ1 sdA
J1 sTa,gTa–
J1 tUmJ1 UrsJ1 xUm

WGN, the Journal of the IMO 37:2 (2009)

Table 3 – Observed parameters of 38 meteor showers. IAU code: number and code of the IAU Meteor Data Center list. λ⊙1 , λ⊙2 : Solar longitude of
the shower activity start and end. λ⊙p : Solar longitude of the shower peak date in 2008. αp , δp : Right ascension and declination of the radiant at its
peak. ∆α, ∆δ: radiant drift in right ascension and declination measured at its peak. The motion of the shower radiant is assumed as a motion along
a great circle of the celestial sphere. The ∆α, ∆δ compose one vector which shows the direction and velocity of the motion at its peak. Therefore
the computation of a radiant position on a specified day becomes rather complex, but it can express the motion in the higher declination region by
only one vector. Vg : geocentric velocity. R: radius of the radiant distribution circle that was allowed for the shower association. ∆V : difference of
Vg that was allowed for the shower. SN2006 is the code which is used by the current UFOOrbitV2.

59

60

WGN, the Journal of the IMO 37:2 (2009)

Figure 5 – Radiants of 24 837 non shower meteors in right ascension and declination.

Figure 6 – Radiants of 24 837 non-shower meteors in coordinates of x-axis: ecliptic longitude λ – solar ecliptic longitude
λ⊙ (λ − λ⊙ ), y-axis: ecliptic latitude. This projection shows the (season independent) solar direction from the Earth (0, 0),
the apex direction (270, 0), and the antihelion direction (180, 0). Most of the radiants occur in the range of λ − λ⊙ = 90
to 270◦ . This almost corresponds to the zenith direction at 18h and 06h local time. The high density area around theapex is the maximum of geocentric velocity and it gradually decreases towards (90, 0). It means that the velocity of the
Earth’s orbital motion dominates the meteor velocity. We find a low-density area around (220, 0). This is the region ofSun-grazing meteors, which are not on stable orbits. The colour version of this Figure can be found on the back cover.

WGN, the Journal of the IMO 37:2 (2009)

61

Table 4 – IAU showers unified to one shower because they
appear as one source in the four-dimensional space.

020 COM, 032 DLM, 090 JCO
016 HYD, 246 AMO
017 NTA, 256 ORN
002 STA, 257 ORS
005 SDA, 003 SIA

6

J4 Com (020 COM)
J4 Hyd (016 HYD)
J4 nTa (017 NTA)
J4 sTa (002 STA)
J4 sdA (005 SDA)

Clustering result

Table 3 and Figure 4 show the result of the clustering.
38 showers were confirmed and their parameters wereobtained. They covered 14 381 meteors and were 37% of
all meteors. It was also confirmed that no concentration
existed on the remaining 63% of meteors on the condition of more than 10 meteors in the range of λ⊙ ±5◦ ,R < 3.0 degree, and ∆V ± 30%, except the image ofthe major showers (Per, Gem, Qua, Ori, Tau) causedby the observation errors. Figures 5 and 6 show theremaining 24 827 meteors.
The comparison with the 56 showers in the IAU listof established showers, shows 24 showers obtained fromthis study correspond to 30 showers in the IAU list.
Another 14 showers found from our analysis are not in
the IAU list, while 26 showers listed in the IAU compilation have not been recognized as concentration in ourdata. A consultation with the IAU MDC yielded eleven
new entries in the working list (numbers 334–344; see
Table 3).
In our catalog, the IAU showers listed in Table 4
were unified to one source because the parameters in thefour-dimensional space gave no reason to divide them.
The Antihelion source as well as the North andSouth Apex, and the Southern Toroidal source were
not confirmed as concentrations. Their borders were
too diffuse to distinguish them from the sporadic background.
It should be noted that there were fuzzy concentrations around the Quadrantids, during November to January. This area overlaps the so called Northern Toroidal
source. In the new catalog, they are divided into three
showers shown in Figure 7. One is the Quadrantids(010 QUA) which is compact and shows a short activity
period. The second cluster which has a slightly higher
velocity and obviously a short activity period was now
included in the working list as number 336 KDR. The
other activity center occurring over a long term waslisted as 334 DAD.
Close to the κ-Cygnids, one early sharp cluster was
extracted and listed as 344 JUG, while others were clustered to one fuzzy shower 012 KCG shown in Figure 8.
The cluster 344 JUG, however, shows an unusual radiant drift and requires further investigation.

Figure 7 – Three showers in the region of the Northern
Toroidal source.

Figure 8 – Clusters of κ-Cygnids.

Sporadic meteors can easily be identified as parts ofshowers if the number of observations is not sufficientand a calibration with the surrounding sporadic meteors has not been done. Showers which have a longactivity period like the Comae Berenicids can easily be(artificially) divided into multiple showers. Applying
an automated clustering on a large data set with too
sensitive clustering conditions may yield hundreds ofmeaningless showers. Therefore, a clustering criterion
is needed to produce a reliable shower list.
In this study, only clear concentrations in the four7 Conclusions
dimensional space that can be thought to maintain a
The determination of a meteor shower is difficult be- relation to their parent objects were considered to because it requires large numbers of accurate observations. showers.

62

WGN, the Journal of the IMO 37:2 (2009)

The 38 showers in the new catalog were obtained
from a uniform procedure based on a larger sample of recent observations than ever previously recorded. Therefore, these data can be assumed to show the recent real
activity of major meteor showers that are optically observable from the northern hemisphere.
The difference between this result and the established IAU list is not small. Further research needs tobe done for 14 new showers which are not in the IAU
list. Ten showers have been included as new entries in
the working list of the IAU MDC. For those 26 showers
in the IAU list which were not confirmed by this study,
a careful study of the activity in recent and future years
should be done.
One of the results of this study, the almost smooth
distribution of sporadic meteors, suggests the possibilityof finding further minor showers or discovering a mechanism responsible for changing sporadic meteor orbits.
Since sporadic meteors can only be obtained by subtraction of the meteors of known showers, however, we needto know more details about the distribution of shower
meteors.
The current study’s results are limited by the detection ability, resolution and accuracy of current video observation. Wider-ranging and longer observations will
reduce the effects of weather and moonlight and enable more precise clustering. Continued observation
and additional research from many regions on the Earthcan be expected to clarify which meteors are associatedwith showers, and to more sharply distinguish showerassociated meteors from sporadic meteors.

Acknowledgements
This study was made possible by the continuous efforts
and contributions of the observers in the SonotaCo Network. I sincerely express my great thanks to the people
listed in Table 2, who observe every night and maketheir results available. Much respect and thanks is also
due to Sirko Molau, the pioneer of video meteor observation who brought me into contact with the IMO.

References
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http://www.astro.amu.edu.pl/∼jopek/MDC2007
Updated 2008 September 29 by T.J. Jopek.
Molau S. and SonotaCo (2008). “On the average altitude of (video) meteors”. WGN, 36, 124–130.
SonotaCo (2005).
“UFCaptureV2 Users Manual”.
http://sonotaco.com/soft/UFO2/help/
english/index.html .
SonotaCo(2007).
“UFOAnalyzerV2”.
http://sonotaco.com/soft/download/
UA2Manual EN.pdf .
SonotaCo (2007b).
“UFOOrbitV2 Users Manual”.
http://sonotaco.com/soft/UO2/
UO21Manual EN.pdf .
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Okamoto S., Masuzawa T., Sekiguchi T., Shimizu
M., and Yamakawa H. (2006). “Detection of October Ursa Majorids in 2006”. WGN, 34, 157–162.
Handling Editor: Jürgen Rendtel