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(meteorobs) Observation December 13/14 2001
Here's my account for the peak night of the Geminids from eastern
Ontario. Standard report follows below...
Thursday evening December 13, I didn't have big hopes for Geminids
peak night. The forecasts were for overcast skies, with chances of
precipitation. The only slightly encouraging sign was a tiny sucker
hole that CMC model showed would developp gradually south-west of
Ottawa. By late evening, the actual weather maps showed no sign of
such a sucker hole yet.
11:30pm, Dec 13...
Despite the conditions, I decide to take off and travel all the way
to JP Bernier's place (South-west of Ottawa) near Franktown. Sky
still completely overcast when I get there near 12:30am. Upon
arriving, I'm greeted by JP who has his backyard observatory wide
open and all ready to start observing. He explains to me that
shortly before I arrived, the sky cleared up in the south and he
could see Orion very well. In the span of a few minutes, he saw a
good handful of meteors. By the time he got ready to start
observing, the sky was suddenly completely overcast again. As we
wait, we're determined that *maybe* we'll have a chance for a clear
break so I proceed to setup my observing coffin, load my camera with
film and leave it on standby. A slightly encouraging sign is to see
Jupiter and a couple of bright stars trying to peak through the
clouds. Too bad it doesn't last for more than a second or two before
they vanish into thicker clouds. We are soon joined by more
observers... also hoping to try and photograph Geminids. We keep
busy with conversations and donuts.
3:00am, Dec 14...
Once a while, a few bright stars try to peak in between the clouds...
"oooohhh!!!"... there goes a bright Geminid right **through** the
clouds. Somebody mentions that a few faint stars are visible very
low in the west. Could it be clearing way down there? As we stare
in that area of the sky, another nice Geminid is well seen plunging
down into the horizon almost disappearing below. We are delighted.
The clearing seems to be growing quickly and we see many more faint
stars! Wow! We scramble to grab our lawn chairs and sit back to
face the western horizon. Somedody is heard saying... "There goes
one!!... "oohh!"... another!!!". We all watch casually for several
minutes, and as the sky clears we count about one Geminid every 30
seconds or so. One of them is a spectacular magnitude -5 blue
fireball that flares twice on its path!! It's well seen by all.
3:30am, Dec 14...
In no time, the entire sky is at least 90% clear. I begin
astrophotography and settle down in my coffin. Limiting magnitude is
now 6.4, and the winter Milky Way is fairly impressive. I "sign-on"
at 3:38am facing the south-west sky. For the next two hours, the sky
remains almost completely clear. All around us, there seems to be
clouds touching the horizons so we appear to be right in the middle
of the sucker hole. Geminids activity is fairly strong with 65 of
them recorded in my first hour. The strongest 10 minute period
occurs between 3:48-3:58am when I count 19 Geminids (average of one
every 30 seconds). The "clustering" effect seems to be present too.
There's four instances of two Geminids appearing within one second of
each other. I also see two instances with Geminids visible within
two seconds. Then there would be a couple of minutes without
activity.
The Geminids were mostly faint, with only a few bright meteors
(nothing brighter than mag -1 when I was recording). The brighter
ones would often be colored blue, yellow or green. One of the
highlights was an intensely colored *electric blue* Geminid of mag 0
that seen crossing near the zenith.
The slight drop in rates during the second hour is probably due to a
number of factors (increasing clouds, sinking radiant in the west and
the exact time of maximum that may have occured a bit earlier than
expected).
I recorded a total of 132 meteors until I was forced to sign-off at
5:41am (local time) due to increasing clouds. This total includes
112 Geminids, 2 Sigma Hydrids, one Chi Orionid and 17 sporadics.
I found it odd to see such a large number of 4th magnitude sporadics.
While recording the activity, I aimed a camera to the north-west sky
and took ten exposures over the course of two hours. I used a 50mm
f1.4 lens and Fuji 800ASA film.
It was a very enjoyable session, and it was certainly well worth the
long wait for the sky to clear!
Pierre Martin
Ottawa, Ontario
DATE: December 13/14 2001
BEGIN: 8:38 UT (3:38 EST) END: 10:41 UT (5:41 EST)
OBSERVER: Pierre Martin (MARPI)
LOCATION: Long: -76.0669 West; Lat: 45.0453 North Elevation:100m
City & Province: Franktown, Ontario, CANADA
RECORDING METHOD: talking clock/tape recorder
-----------------------------------------------------------------------
OBSERVED SHOWERS: 3-letter code; radiant position
GEM (Geminids) 0728 +33
MON (Monocerotids) 0700 +08
XOR (chi Orionids) 0636 +23
HYD (Sigma Hydrids) 0844 +01
Napx (north apex) or COM 1136 +17
Sapx (south apex) 1136 -13
SPO (sporadics) -
-----------------------------------------------------------------------
OBSERVING PERIODS: 0 = none seen; / = shower not observed
PERIOD(UT) FIELD Teff LM SPO GEM HYD XOR MON Napx Sapx
08:38-09:38 0816 +09 1.00 6.45 6 65 1 1 0 2 1
09:38-10:41 0858 +11 0.93 6.08 4 47 1 0 0 1 3
-------------------------------------------------------------
TOTALS: 1.93 10 112 2 1 0 3 4 = 132
-------------------------------------------------------------
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 I did not
spent looking at the sky). One hour = 1.00 teff. The fourth column
(LM) is the average naked eye limitimg magnitude, determined by
triangle star counts. All following columns indicate the number of
meteors for each shower observed.
MAGNITUDE DISTRIBUTIONS:
SHOWER -1 0 +1 +2 +3 +4 +5 AVERAGE
SPO 0 0 0 0 2 12 3 +4.06
GEM 4 9 8 23 20 28 20 +2.88
HYD 0 0 0 0 0 2 0 +4.0
XOR 0 0 0 0 1 0 0 +3.0
---------------------------------
TOTALS: 4 9 8 23 23 42 23
---------------------------------
Note: Magnitude scale is to determine the brightness of sky objects.
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 for showers.
SKY OBSCURED:
15% from 10:10 to 10:21 UT
------------------------
Dead time: 7 minutes
Breaks (UT): 10:22-10:24, 10:31-10:36
---------------------------------------------------------------------
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