(meteorobs) Geminids III -- 2007 Dec 14/15

[Bruce McCurdy]

            While I had hoped to observe the 2007 Geminids ramping up from 
one night to the next, December skies had other ideas, wiping out the 12th 
through the 14th. However, it cleared off on Friday evening and I headed out 
to Beaver Hills Dark Sky Preserve roughly half a day past the predicted 
peak. I arrived a little before 21:00 local time on what was a regular 
observing night for RASC Edmonton Centre, with about eight club members 
present in -20° C. conditions. Of course those who had arrived earlier 
immediately regaled me with reports of all the fireballs they had seen in 
the early evening sky. While I was the only dedicated meteor observer as the 
others were primarily observing with telescopes, I heard numerous 
exclamations around the parking lot throughout the evening as people (often 
in concert with my car radio) spotted another bright Gem or Ant.
            Sky conditions were fair, with bright snow cover reducing 
limiting magnitude to around 5.8. I settled in to my sleeping bag and 
observing chair at 4h UT and immediately observed a mag -2 Geminid which was 
a harbinger of an excellent first hour and a pretty good night. In five 
hours Teff I observed 150 meteors including 93 Geminids. Fully 45 of these, 
including 29 Gems, were zeroeth magnitude or brighter, although I saw 
nothing that I considered a true fireball, with just one meteor as bright as 
mag -3. But I had no complaints given the average magnitude of all meteors 
on the night was an impressive +1.7. The first and third hours were 
particularly good in this respect.
            Despite their brightness only a handful of Geminids had any sort 
of persistent train, which is consistent with my past experience with this 
shower. On the other hand, I was fortunate to see a number of bright 
Antihelions on this night, many of which did feature persistent trains of a 
second or more. I don't remember ever having as many as 8 Antihelions in an 
hour before, nor 17 in a night, and with an average magnitude of +1.0 at 
that. By the last hour that source finally dried up, but there was a 
moderately strong showing of 6 Coma Berenicids, most of them relatively 
faint. Meanwhile the Hydrids were neither numerous nor bright, but all 
Geminid week I was exclaiming into my tape recorder about how pretty they 
were. (I saw a dozen of them in ten hours Teff over three nights.) Even 
those of third magnitude seemed to leave nice trains.
            Given the unwieldy numbers -- my highest count of the year by 
far, more than my next two best nights combined -- I will refrain from a 
meteor-by-meteor play-by-play (available off-list if somebody really needs 
it), and will post below hourly summaries of this night's enumeration.
            I will comment on one meteor I didn't see. At 0914 UT Larry Wood 
was the last of the telescopic observers to make his way out of the parking 
lot while I stayed to complete my fifth and final hour. As he headed north 
to the exit I faced south to avoid any accidental white light. Well, he 
moved about a metre and slammed on his brakes and honked the horn and 
without rolling down the window I could hear him holler "Did you see 
THAT??!!" which of course I hadn't. THAT turned out to be a -5 fireball with 
a spectacular explosion point. According to Larry.
            Come to think of it, maybe he didn't slam on the brakes, and 
that "white light violation" that flashed on the snow was actually the 
bolide I was destined to miss. Ah well, I've often compared meteor observing 
to fishing, and sometimes the best fish stories are about the one that got 
away. Not that I'm complaining, my basket was pretty full on this night.

            Bruce
            *****

Observer: Bruce McCurdy, MCCBR
Location: Beaver Hills Dark Sky Preserve (Blackfoot), IMO code 51128
53° 32' 12" N., 112° 46' 48" W., elevation 711 metres
Date: 2007 December 15, 04:00 - 09:45 UT, Teff = 5.0 hours
Limiting magnitude 5.7 to 5.8 throughout (SQM 20.9 to 21.0)
Primary method: visual, microcassette recorder and talking watch
Secondary method: audio, monitoring forward scatter by car radio (FM 94.5)

Active radiants:
Antihelion (ANT) - 06:28 (097) +23
Monocerotids (MON) 07:00 (105) +08
Geminids (GEM) 07:36 (114) +33
Sigma Hydrids (HYD) 08:44 (131) +01
Coma Berenicids (COM) 11:32 (173) +26

Hour 1: 04:00-05:00 UT; clear; LM = 5.8; facing SSE 60°; Teff = 1.0 hour
8 ANT: -1(2), 0, +2(2), +3(3)
0 MON
24 GEM: -3, -1(4), 0(3), +1(3), +2(5), +3(7), +4
0 HYD
0 COM
8 SPO: -2(2), 0, +3(3), +4(2)
Total meteors: forty
***

Hour 2: 05:00-06:00 UT; clear; LM = 5.7; facing SSE 60°; Teff =1.0 hour
3 ANT: 0, +2, +3
0 MON
16 GEM: -1(2), 0(2), +1(2), +2(3), +3(4), +4(2), +5
0 HYD
0 COM
8 SPO: -2, +2(2), +3, +4(3), +5
Total meteors: twenty-seven
***

Hour 3: 06:00-07:00 UT; clear; LM = 5.7; SSE 60°; Teff =1.0 hour
3 ANT: -2, -1, +2
1 MON: 0
15 GEM: -2(2), -1(2), 0(4), +1, +2(2), +3(4)
1 HYD: +3
0 COM
6 SPO: 0(2), +3(3), +4
Total meteors: twenty-six
***

Hour 4: 07:20-08:20 UT; clear; LM = 5.8; SSE 60°; Teff = 1.0 hour
3 ANT: 0(2), +2
2 MON: +2, +4
19 GEM: -2, -1(3), +1(3), +2(5), +3(3), +4(4)
0 HYD
1 COM: +2
2 SPO: -1, +4
Total meteors: twenty-seven
***

Hour 5: 08:25-09:45 (with 20-minute break); clear; LM = 5.8; E. 60°; Teff = 
1.0 hour
0 ANT
1 MON: +1
19 GEM: -2, -1(2), 0(2), +1(3), +2(3), +3(4), +4(3), +5
2 HYD: +2, +3
6 COM: +1, +3(3), +4(2)
2 SPO: +4(2)
Total meteors: thirty
***

Observing summary: 04:00-09:45; clear; avg. LM = 5.8; Teff = 5.0 hours
17 ANT: -2, -1(3), 0(4), +2(5), +3(4)    [Avg. = +1.0]
4 MON: 0, +1, +2, +4     [Avg. = +1.8]
93 GEM: -3, -2(4), -1(13), 0(11), +1(12), +2(18), +3(22), +4(10), +5  [Avg. 
= +1.5]
3 HYD: +2, +3(2)     [Avg. = +2.7]
7 COM: +1, +2, +3(3), +4(2)     [Avg. = 2.9]
26 SPO: -2(3), -1, 0(3), +2(2), +3(7), +4(9), +5     [Avg. = +2.3]
Total meteors: one hundred fifty
*****