International Meteor Organization
Remarks, Abbreviations, Tables
Radiant sizes and meteor plotting
If you are not observing during a major-shower maximum, it is essential to associate meteors with their radiants correctly, since the total number of meteors will be small for each source. Meteor plotting allows shower association by more objective criteria after your observation than the simple imaginary back-prolongation of paths under the sky. With meteors plotted on gnomonic maps, you can trace them back to their radiants by extending their straight line paths. If a radiant lies on another chart, you should find common stars on an adjacent chart to extend this back-prolongation correctly.
How large a radiant should be assumed for shower association? The real physical radiant size is very small, but visual plotting errors cause many true shower meteors to miss this real radiant area. Thus we have to assume a larger effective radiant to allow for these errors. Unfortunately, as we enlarge the radiant, so more and more sporadic meteors will appear to line up accidentally with this region. Hence we have to apply an optimum radiant diameter to compensate for the plotting errors loss, but which will not then be swamped by sporadic meteor pollution. Table 1 gives this optimum diameter as a function of the distance of the meteor from the radiant.
Table 1: Optimum radiant diameters to be assumed for shower association of minor-shower meteors as a function of the radiant distance D of the meteor.
D optimum
diameter
15° 14°
30° 17°
50° 20°
70° 23°
The path-direction is not the only criterion for shower association. The angular velocity of the meteor should match the expected speed of the given shower meteors according to their geocentric velocities. Angular velocity estimates should be made in degrees per second (°/s). To do this, make the meteors you see move for one second in your imagination at the speed you saw them. The path length of this imaginary meteor is the angular velocity in °/s. Note that typical speeds are in the range 3°/s to 25°/s. Typical errors for such estimates are given in Table 2.
Table 2: Error limits for the angular velocity.angular velocity °/s 5 10 15 20 30 permitted error °/s 3 5 6 7 8
In you found a meteor which hits the radiant within the above diameter, check its angular velocity. Table Table 3 gives the angular speeds for a few geocentric velocities, which can be looked up in Table 5 for each shower.
Table 3: Angular velocities as a function of the radiant distance of the meteor and the elevation of the meteor for three different geocentric velocities. All velocities are in °/s. The tables are symmetric in D and h.
V=25 km/s V=40km/s V=60km/s
D 10° 20° 40° 60° 90° 10° 20° 40° 60° 90° 10° 20° 40° 60° 90°
10° 0.4 0.9 1.6 2.2 2.5 0.7 1.4 2.6 3.5 4.0 0.9 1.8 3.7 4.6 5.3
20° 0.9 1.7 3.2 4.3 4.9 1.4 2.7 5.0 6.8 7.9 1.8 3.5 6.7 9.0 10.0
40° 1.6 3.2 5.9 8.0 9.3 2.6 5.0 9.5 13.0 15.0 3.7 6.7 13.0 17.0 20.0
60° 2.2 4.3 8.0 11.0 13.0 3.5 6.8 13.0 17.0 20.0 4.6 9.0 17.0 23.0 26.0
90° 2.5 4.9 9.3 13.0 14.0 4.0 7.9 15.0 20.0 23.0 5.3 10.0 20.0 26.0 30.0
Abbreviations
alpha, delta: Coordinates for a shower's radiant position, usually at maximum; alpha is right ascension, delta is declination. Radiants drift across the sky each day due to the Earth's own orbital motion around the Sun, and this must be allowed for using the details in Table 6 for nights away from the listed shower maxima.
r: The population index, a term computed from each shower's meteor magnitude distribution. r = 2.0-2.5 is brighter than average, while r above 3.0 is fainter than average.
sol: Solar longitude, a precise measure of the Earth's position on its orbit which is not dependent on the vagaries of the calendar. All sol are given for the equinox J2000.0.
V: Atmospheric or meteoric velocity given in km/s. Velocities range from about 11 km/s (very slow) to 72 km/s (very fast). 40 km/s is roughly medium speed.
ZHR: Zenithal Hourly Rate, a calculated maximum number of meteors an ideal observer would see in perfectly clear skies with the shower radiant overhead. This figure is given in terms of meteors per hour. Where meteor activity persisted at a high level for less than an hour, an estimated ZHR (EZHR) is used measuring the activity as if it would have lasted for an hour.
TFC and PFC: suggested telescopic and small-camera photographic field centers respectively. beta is the observer's latitude ("<" means "south of" and ">" means "north of"). Pairs of telescopic fields must be observed, alternating about every half hour, so that the positions of radiants can be defined. The exact choice of TFC or PFC depends on the observer's location and the elevation of the radiant. Note that the TFCs are also useful centers to use for video camera fields as well.
Tables
Table 4: Lunar phases for 2004.
New First Full Last
Moon Quarter Moon Quarter
January 6 January 15
January 21 January 29 February 6 February 13
February 20 February 29 March 6 March 13
March 20 March 28 April 5 April 12
April 19 April 27 May 4 May 11
May 19 May 27 June 3 June 9
June 17 June 25 July 2 July 9
July 17 July 25 July 31 August 7
August 16 August 23 August 30 September 6
September 14 September 21 September 28 October 6
October 14 October 20 October 28 November 5
November 12 November 19 November 26 December 5
December 12 December 18 December 26
Table 5: Working list of visual meteor showers. Details in this Table
correct according to the best information available in June 2003. Contact
the IMO's Visual Commission for more information. Maximum dates in
parentheses indicate reference dates for the radiant, not true maxima. Some
showers have ZHRs that vary from year to year. The most recent reliable
figure is given here, except for possibly periodic showers that are noted
as "var." = variable. An asterisk (*) in the sol column indicates the shower may have other or additional peak
times, noted in the text.
Shower Activity Maximum Radiant V r ZHR IMO
Period Date sol alpha delta Code
° ° ° km/s
Quadrantids Jan 01-Jan 05 Jan 04 283.16 230 +49 41 2.1 120 QUA
delta-Cancrids Jan 01-Jan 24 Jan 17 297 130 +20 28 3.0 4 DCA
alpha-Centaurids Jan 28-Feb 21 Feb 08 319.2 210 -59 56 2.0 6 ACE
delta-Leonids Feb 15-Mar 10 Feb 25 336 168 +16 23 3.0 2 DLE
gamma-Normids Feb 25-Mar 22 Mar 13 353 249 -51 56 2.4 8 GNO
Virginids Jan 25-Apr 15 (Mar 24)(004) 195 -04 30 3.0 5 VIR
Lyrids Apr 16-Apr 25 Apr 23 032.1 271 +34 49 2.1 18 LYR
pi-Puppids Apr 15-Apr 28 Apr 24 033.5 110 -45 18 2.0 var. PPU
eta-Aquarids Apr 19-May 28 May 05 045.5 338 -01 66 2.4 60 ETA
Sagittarids Apr 15-Jul 15 (May 19)(059) 247 -22 30 2.5 5 SAG
June Bootids Jun 26-Jul 02 Jun 27 095.7 224 +48 18 2.2 var. JBO
Pegasids Jul 07-Jul 13 Jul 09 107.5 340 +15 70 3.0 3 JPE
July Phoenicids Jul 10-Jul 16 Jul 13 111 032 -48 47 3.0 var. PHE
Pisces Austrinids Jul 15-Aug 10 Jul 27 125 341 -30 35 3.2 5 PAU
Southern delta-Aquarids Jul 12-Aug 19 Jul 27 125 339 -16 41 3.2 20 SDA
alpha-Capricornids Jul 03-Aug 15 Jul 29 127 307 -10 23 2.5 4 CAP
Southern iota-Aquarids Jul 25-Aug 15 Aug 04 132 334 -15 34 2.9 2 SIA
Northern delta-Aquarids Jul 15-Aug 25 Aug 08 136 335 -05 42 3.4 4 NDA
Perseids Jul 17-Aug 24 Aug 12 140.0 046 +58 59 2.6 110 PER
kappa-Cygnids Aug 03-Aug 25 Aug 17 145 286 +59 25 3.0 3 KCG
Northern iota-Aquarids Aug 11-Aug 31 Aug 19 147 327 -06 31 3.2 3 NIA
alpha-Aurigids Aug 25-Sep 08 Aug 31 158.6 084 +42 66 2.6 7 AUR
delta-Aurigids Sep 05-Oct 10 Sep 09 166.7 060 +47 64 2.9 5 DAU
Piscids Sep 01-Sep 30 Sep 19 177 005 -01 26 3.0 3 SPI
Draconids Oct 06-Oct 10 Oct 08 195.4 262 +54 20 2.6 var. GIA
epsilon-Geminids Oct 14-Oct 27 Oct 18 205 102 +27 70 3.0 2 EGE
Orionids Oct 02-Nov 07 Oct 21 208 095 +16 66 2.5 23 ORI
Southern Taurids Oct 01-Nov 25 Nov 05 223 052 +13 27 2.3 5 STA
Northern Taurids Oct 01-Nov 25 Nov 12 230 058 +22 29 2.3 5 NTA
Leonids Nov 14-Nov 21 Nov 17 235.27 153 +22 71 2.5 50+ LEO
alpha-Monocerotids Nov 15-Nov 25 Nov 21 239.32 117 +01 65 2.4 var. AMO
chi-Orionids Nov 26-Dec 15 Dec 01 250 082 +23 28 3.0 3 XOR
Phoenicids Nov 28-Dec 09 Dec 06 254.25 018 -53 22 2.8 var. PHO
Puppid-Velids Dec 01-Dec 15 (Dec 06)(255) 123 -45 40 2.9 10 PUP
Monocerotids Nov 27-Dec 17 Dec 08 257 100 +08 42 3.0 3 MON
sigma-Hydrids Dec 03-Dec 15 Dec 11 260 127 +02 58 3.0 2 HYD
Geminids Dec 07-Dec 17 Dec 13 262.2 112 +33 35 2.6 120 GEM
Coma Berenicids Dec 12-Jan 23 Dec 19 268 175 +25 65 3.0 5 COM
Ursids Dec 17-Dec 26 Dec 22 270.7 217 +76 33 3.0 10 URS
Table 6: Radiant positions during the year in alpha and delta.
COM DCA QUA
Jan 0 186 +20 112 +22 228 +50
Jan 5 190 +18 116 +22 231 +49
Jan 10 194 +17 121 +21
Jan 20 202 +13 130 +19 ACE VIR
Jan 30 200 -57 157 +16 DLE
Feb 10 214 -60 165 +10 155 +20 GNO
Feb 20 225 -63 172 +6 164 +18 225 -53
Feb 28 178 +3 171 +15 234 -52
Mar 10 186 0 180 +12 245 -51
Mar 20 192 -3 256 -50
Mar 30 198 -5
Apr 10 SAG LYR PPU 203 -7
Apr 15 224 -17 263 +34 106 -44 ETA 205 -8
Apr 20 227 -18 269 +34 109 -45 323 -7
Apr 25 230 -19 274 +34 111 -45 328 -5
Apr 30 233 -19 332 -4
May 5 236 -20 337 -2
May 10 240 -21 341 0
May 20 247 -22 350 +5
May 30 256 -23
Jun 10 265 -23
Jun 15 270 -23
Jun 20 275 -23 JBO
Jun 25 280 -23 223 +48
Jun 30 284 -23 225 +47 CAP JPE
Jul 5 289 -22 285 -16 SDA 338 +14
Jul 10 293 -22 PHE 289 -15 325 -19 NDA 341 +15 PER PAU
Jul 15 298 -21 032 -48 294 -14 329 -19 316 -10 012 +51 330 -34
Jul 20 299 -12 333 -18 319 -9 SIA 018 +52 334 -33
Jul 25 303 -11 337 -17 323 -9 322 -17 023 +54 338 -31
Jul 30 KCG 308 -10 340 -16 327 -8 328 -16 029 +55 343 -29
Aug 5 283 +58 NIA 313 -8 345 -14 332 -6 334 -15 037 +57 348 -27
Aug 10 284 +58 317 -7 318 -6 349 -13 335 -5 339 -14 043 +58 352 -26
Aug 15 285 +59 322 -7 352 -12 339 -4 345 -13 050 +59
Aug 20 286 +59 327 -6 AUR 356 -11 343 -3 057 +59
Aug 25 288 +60 332 -5 076 +42 347 -2 065 +60
Aug 30 289 +60 337 -5 082 +42 DAU
Sep 5 088 +42 055 +46 SPI
Sep 10 060 +47 357 -5
Sep 15 066 +48 001 -3
Sep 20 071 +48 005 -1
Sep 25 NTA STA 077 +49 009 0
Sep 30 021 +11 023 +5 ORI 083 +49 013 +2
Oct 5 025 +12 027 +7 085 +14 089 +49 GIA
Oct 10 029 +14 031 +8 088 +15 095 +49 EGE 262 +54
Oct 15 034 +16 035 +9 091 +15 099 +27
Oct 20 038 +17 039 +11 094 +16 104 +27
Oct 25 043 +18 043 +12 098 +16 109 +27
Oct 30 047 +20 047 +13 101 +16
Nov 5 053 +21 052 +14 105 +17
Nov 10 058 +22 056 +15 LEO AMO
Nov 15 062 +23 060 +16 150 +23 112 +2
Nov 20 067 +24 064 +16 XOR 153 +21 116 +1
Nov 25 072 +24 069 +17 075 +23 120 0 MON PUP PHO
Nov 30 080 +23 HYD 091 +8 120 -45 014 -52
Dec 5 COM GEM 085 +23 122 +3 096 +8 122 -45 018 -53
Dec 10 169 +27 108 +33 090 +23 126 +2 100 +8 125 -45 022 -53
Dec 15 173 +26 113 +33 094 +23 130 +1 URS 104 +8 128 -45
Dec 20 177 +24 118 +32 217 +75
Table 7: Working list of daytime radio meteor streams. The "Best Observed"
columns give the approximate local mean times between which a four-element
antenna at an elevation of 45° receiving a signal from a 30-kW transmitter
1000 km away should record at least 85% of any suitably positioned radio-
reflecting meteor trails for the appropriate latitudes. Note that this is
often heavily dependent on the compass direction in which the antenna is
pointing, however, and applies only to dates near the shower's maximum.
Shower Activity Max sol Radiant Best Observed Rate
Date 2000.0 al. de. 50°N 35°S
° ° °
Cap/Sagittarids Jan 13-Feb 04 Feb 02 312.5 299 -15 11h-14h 09h-14h medium
chi-Capricornids Jan 29-Feb 28 Feb 14 324.7 315 -24 10h-13h 08h-15h low
Piscids (April) Apr 08-Apr 29 Apr 20 030.3 007 +7 07h-14h 08h-13h low
delta-Piscids Apr 24-Apr 24 Apr 24 034.2 011 +12 07h-14h 08h-13h low
epsilon-Arietids Apr 24-May 27 May 09 048.7 044 +21 08h-15h 10h-14h low
Arietids (May) May 04-Jun 06 May 16 055.5 037 +18 08h-15h 09h-13h low
omicron-Cetids May 05-Jun 02 May 20 059.3 028 -4 07h-13h 07h-13h medium
Arietids May 22-Jul 02 Jun 07 076.7 044 +24 06h-14h 08h-12h high
zeta-Perseids May 20-Jul 05 Jun 09 078.6 062 +23 07h-15h 09h-13h high
beta-Taurids Jun 05-Jul 17 Jun 28 096.7 086 +19 08h-15h 09h-13h medium
gamma-Leonids Aug 14-Sep 12 Aug 25 152.2 155 +20 08h-16h 10h-14h low
Sextantids Sep 09-Oct 09 Sep 27 184.3 152 0 06h-12h 06h-13h medium
Useful addresses
For more information on observing techniques, and when submitting results, please contact the appropriate IMO Commission Director:
Fireball Data Center : André Knöfel, Saarbrückerstraße 8,
(FIDAC) D-40476 Düsseldorf, Germany.
(e-mail: fidac@imo.net)
Photographic Commission: Marc de Lignie, Prins Hendrikplein 42,
NL-2264 SN Leidschendam, the Netherlands.
(e-mail: m.c.delignie@xs4all.nl)
Radio Commission: Temporarily vacant
(e-mail: radio@imo.net)
Telescopic Commission: Malcolm Currie, 25 Collett Way,
Grove, Wantage, Oxfordshire, OX12,0NT, UK.
(e-mail: tele@imo.net)
Video Commission: Sirko Molau, Verbindungsweg 7,
D-15366 Hönow, Germany
(e-mail: video@imo.net)
Visual Commission: Rainer Arlt, Friedentraße 5,
D-14109 Berlin, Germany
(e-mail: visual@imo.net)
or contact IMO's Homepage in the World-Wide-Web: http://www.imo.net/
For further details on IMO membership, please write to:
Ina Rendtel, IMO Treasurer, Mehlbeerenweg 5,
D-14469 Potsdam, Germany.
(e-mail: treasurer@imo.net)
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