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(meteorobs) Re: NM REPOST full moon and LM
Back on 1997 Apr 3 there was some discussion about full moon and LM. Here
is a repost of what I said then :
From Rainer :
>
>I fully agree that lm correction under such bad conditions like a full moon
>becomes most uncertain. But I have to admit that I have never experienced 4.0
>skies under full moon. My general difference to normal skies is 1mag. I have
>about 6.2 under countryside skies, ~5.2 under full moon. The lm factor is 3.3
>then, which sounds suitable compared to the above 5met/hr. Where does the
>4.0-under-full-moon come from?
>
With a full moon high in the sky I typically experience a limiting magnitude
around 4.0. About two hours before moonset it improves to 5.0, then the
final hour (if there's enough dark time left) it gets toward 6.0.
Geminids with a full moon (or very close to) several times I had a 4.0 sky
and consistently 18 Geminids/hour. My dark-sky rate (7.0 sky) is in the
80's, so the correction factor from 4.0 to 7.0 is thus 4 to 5. No fancy
algebra or theory involved, just a simple ratio of dark sky vs. bright sky
rates.
Perseids under similar conditions in 1984 I saw 9/hour for 3 straight hours.
A normal Perseid shower back then was around 40/hour ; again the correction
factor is between 4 and 5.
Rainer is quite a ways further north than I am, so he won't see the moon as
high as I will, on average. That ought to account for his better LM under
such conditions. A winter full moon passes overhead here ; I have seen it
go NORTH of the zenith in the extreme years 1969 and 1988. It's blazing
bright when straight up -- there's no way you're going to get 5.0 at this time.
Norman
Norman W. McLeod III
Staff Advisor
American Meteor Society
Fort Myers, Florida
nmcleod@peganet.com
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