(meteorobs) Observation December 14/15 2007

[Pierre Martin]

Here's my full summary report for the post-max night of Geminids.   
Todd Weeks and I left Ottawa early in the evening for some supper,  
and to look for an observing site about an hour's drive east of  
Ottawa.  The wind was gusting to 50km/hr and the temperature plunging  
fast, so I was not too sure what to expect.  The wind just didn't  
seem to let up!  Many roads had become poor to drive on due to  
drifting snowbanks and blowing snow.  The first site that we got to  
had gorgeous horizons in all directions.  It would have been great  
but the very nasty windchill from gusting winds made it very  
unpleasant to stay outside our cars for more than an instant!  So we  
back-tracked a bit west to a quiet road next to a line of trees from  
a forest.  It still had a fine eastern horizon - we were hoping that  
the trees would block the worse effects of the westerly wind.  When  
we arrived, we were surprised at how quiet it was... Either the trees  
were doing a remarkably good job, or the wind had suddenly died.  The  
lack of wind sure made all the difference, so we setup.  Todd was  
soon sitting down in his chair to enjoy the Geminids, while I spent  
the next little while setting up my mount and cameras.  My mount's  
power cable broke, so tracking was not going to be possible (with no  
other solution, I re-set the cameras to do shorter timed exposures).   
While I was doing this, Todd was shouting as a number of nice  
Geminids streaked overhead, even though the radiant was still quite low.

I signed on at 10pm EST, and observed for four hours until after  
2am.  It was another very cold night down to -18C, but did not feel  
nearly as brutal as it did two nights ago.  The sky had a LM=6.3, and  
average quality transparency.

Geminids were active as follows for each hour... 44, 37, 36 and 18.   
It was very apparent that the Earth was exiting the Geminids stream  
by the fourth hour.  As is often typical during the hours after the  
peak, the Geminids were clearly in a period of high meteor  
brightness.  Some terrific meteors were seen, which made this session  
quite entertaining.  Out of a total of 135 Geminids, the average  
meteor magnitude was +2.11, which is more than a full magnitude  
brighter than what I got two nights ago.  No less than 43 of these  
were mag +1 or brighter, and 17 of them were in the negative magnitudes.

The most impressive Geminid came at 12:27am... It was an intense blue- 
white mag -5 fireball that dropped towards the eastern horizon over a  
30 degrees path!  It fragmented with several tiny pieces along its  
path... very memorable!

Geminids left few or no trains.  The longest lasting trains from the  
brightest meteors were only 1 sec or less.  The most frequent colors  
that I was seeing in the brighter meteors was blue-white, yellow,  
blue, blue-green and even pure white.

Sporadics doubled in numbers each hour until the third hour - then  
they were almost absent.  Only weak activity was noticed from the  
other active radiants.

Three swift moving meteors were seen again radiating from Ursa Major.

With another major winter snowstorm coming our way, this is it with  
the Geminids for me.  I'm hoping to catch perhaps a tail-end of the  
predicted Ursids outburst next week - I definitely plan to give it a  
try despite the Moon.

Pierre Martin
Ottawa, Ontario


DATE: December 14/15 2007
BEGIN: 0300 UT (2200 EST) END: 0715 UT (0215 EST)
OBSERVER: Pierre Martin (MARPI)
LOCATION: Long: -75.104 West; Lat: 45.434 North
City & Province: Bourget, Ontario, CANADA
RECORDING METHOD: talking clock, tape recorder, cord align
----------------------------------------------------------

OBSERVED SHOWERS:______________________________radiant position
MON (Monocerotids)_____________________________07:00 (105) +08
GEM (Geminids)_________________________________07:36 (114) +33
HYD (Sigma Hydrids)____________________________08:44 (131) +01
COM (Coma Berenicids)__________________________11:32 (173) +26
ANT (antihelions)______________________________06:28 (097) +23
SPO (sporadics)
----------------------------------------------------------

OBSERVING PERIODS: 0 = none seen; / = shower not observed

PERIOD(UT)___FIELD____Teff____F______LM____SPO_GEM_MON_HYD_COM_ANT

0300-0400___0735+31___1.00___1.00___6.30____3__44___1___0___0___1
0400-0500___0838+32___0.99___1.00___6.30____6__37___1___1___0___1
0500-0617___0931+33___0.98___1.00___6.35___12__36___0___1___0___0
0617-0715___1050+32___0.97___1.00___6.40____3__18___0___1___2___1

TOTALS:_______________3.94_________________24__135__2___3___2___3  = 169

Note: The first column (Period UT) refers to observing periods broken  
down as close as possible to one hour of true observing, in Universal  
Time. The second column (Field) is the area in in the sky where I  
centered my field of view. The third column (TEFF) represents  
effective observing time (corrected for breaks or any time not spent  
looking at the sky). The column (LM) is the average naked eye  
limiting magnitude, determined by triangle star counts. All following  
columns indicate the number of meteors for each shower observed.
------------------------

MAGNITUDE DISTRIBUTIONS:

SHOWER
______-5__-4__-3__-2__-1___0__+1__+2__+3__+4__+5__+6______AVE

GEM____1___0___3___7___6__12__14__23__30__28___9___2_____+2.11
SPO____0___0___0___0___0___0___0___5___6__10___3___0_____+3.46
ANT____0___0___0___0___0___0___1___1___0___1___0___0_____+2.33
HYD____0___0___0___0___0___0___0___1___1___1___0___0_____+3.00
MON____0___0___0___0___0___0___0___0___1___1___0___0_____+3.50
COM____0___0___0___0___0___0___0___0___0___2___0___0_____+4.00

Note: Magnitude -8 is comparable to a quarter moon, magnitude -4 with  
the planet Venus, magnitude -1 with the brightest star Sirius,  
magnitude +2 to +3 with most average naked eye stars and magnitude +6  
to +7 are the faintest stars the naked eye can see under typical dark  
conditions. A meteor of at least magnitude -3 is considered a  
fireball. The above table contains the magnitudes from all observed  
meteors, and the average (last column) for showers.
------------------------

SKY OBSCURED (FOV) (UT):  none

------------------------

Dead time: 18.5 min (breaks)

Breaks (UT): 4:56 (30sec), 5:05-21, 5:30-32