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(meteorobs) re:Quadrantids good from SW Florida
At long last I have seen an excellent Quadrantid display : 1997 Jan 2/3.
This must be a once-in-a-generation event. I began active observing free of
school in 1971, and 26 years later all factors came together for the Quads.
Time observed 6.38 hours with 150 Quads and 30 sporadics seen. The
beneficial midnight clouds came through again and left in good time,
retarding the fog until dawn. Only then did it get rather thick, and it
remained shallow in height.
The best period was 456-620 EST (956-1120 UT), when the pace increased very
suddenly, with sky LM6.0 and 86 Quads seen (61/hour).
A short evening watch from the rooftop failed to get an early Quad. Jan 2/3
rates :
630-744 UT 345,+40 1.23hrs F1.00 LM5.0 0 QUA 2 SPOR 2 TOT
624-726 UT 90,+40 1.03hrs F0.70 LM7.0 3 QUA 5 SPOR 7 TOT
726-826 UT 105,+40 1.00hrs F1.00 LM6.0 16 QUA 4 SPOR 20 TOT
826-926 UT 120,+40 1.00hrs F1.00 LM6.0 28 QUA 6 SPOR 34 TOT
926-956 UT 125,+40 0.50hrs F0.75 LM5.8 9 QUA 1 SPOR 10 TOT
956-1120 UT 140,+40 1.40hrs F1.00 LM6.0 86 QUA 12 SPOR 98 TOT
Also watched 9 more minutes into increasing twilight and saw 8 more Quadrantids.
Using only Quads seen in 6.0 sky and not behind clouds and haze, the
magnitude distribution is:
-2 : 4
-1 : 8
0 : 15
1 : 16
2 : 26
3 : 23
4 : 23
5 : 14
Total is 129 Quadrantids from just 6.0 sky averaging 2.19. No fireballs.
Only 6 Quads had trains, all 1 second. Non-white colors from all conditions
comprise 49 yellow, 3 orange, 13 blue, and 1 blue-green. So much for the
Quadrantids being a shower of "bluish" meteors. Somebody that sees only
blue meteors got that into print years ago, and it became lodged in general
descriptions. Once something appears in print, it becomes accepted as gospel
and is thereafter very difficult to get corrected.
I started writing this several hours ago, then various things intervened.
It came time to observe an hour from the roof again. Jan 3/4 at 631-736 EST
only one +2 sporadic seen, sky 5.0. So no evening Quadrantid this year.
The chance of seeing one this early must be better when the peak occurs at
this time.
I have calculated a preliminary ZHR using my sky correction factors for
sporadics. (A Quadrantid factor will be developed later.) A 6.0 sky has
0.616 times the meteors of a 7.0 sky ; and a 6.5 sky 0.860 times. Hence, a
6.0 sky has (0.616/0.860) times the meteors of a 6.5 sky, or 0.716. ( I have
many more years of data to refine these values eventually.) The usual ZHR
formula is all right for a radiant altitude of 45 degrees, the sine of which
is 0.707. So, the ZHR is,
86 observed meteors / (1.40 hours X 0.716 X 0.707) = 121. The sky
correction is too strong for a shower, and the radiant may be slightly lower
than I used, so the inaccuracies largely offset. Thus, 121 is a believable
value for the ZHR, and, for a change, agrees well with the value often used
today.
We need someone from Texas or further west to tell us when the heavy rates
ended. Hopefully we will find out.
Norman
Fort Myers, Florida