Remarks, Abbreviations, Tables 2004

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)  
   
  

Please try to enclose return postage when writing to any IMO officials,
either in the form of stamps (same country only) or as an International
Reply Coupon (I.R.C. – available from main postal outlets). Thank you!