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RE: (meteorobs) Leonid eZHR question, plus others



On Wed, 21 November 2001, Wayne T Hally wrote:
> 
> Ed, be sure your Sine angle is in radians if that's what your calculator 
> requires.

I think this is supposed to be degrees.  Makes sense in both the NAMN example and the table at:

http://www.imodot net/visual/major01.html#table1

LM = +4.2 gives a major correction to the hourly (or effective hourly) rate (about 5x).  So, the EZHR is very high, but is based on a very small sample size. 

And, as Wayne says, a one-minute sample from one observer is simply not significant.  My highest minute count was 32, however just before that I got 9. It's probably just a matter of sampling.  I'll have to see if I can hear someone else counting in the background noise of that 9-Leonid minute on my tape (confirming that they were seeing meteors that I wasn't). 

On a raw level, 5-minute intervals seem to communicate best what I saw as far as peak times, but are still too small by themselves to provide meaningful ZHRs. Especially with Rainer's notes about variation in perception, it's best to wait for a rigorous analysis of many observations. 

> Other questions.  First, I was wondering how to deal with fog. My LM at 11:00 UTC was about 4.0, but I could see the really bright ones down low in the sky.  So I think that F=1.0, but the
> sky wasn't really "unobstructed".  Is there a transparency
> factor?  Or maybe that's in the LM value?

Big problem.  I ran into it as well (not fog but moving cirrostratus) and even commented to another observer afterward that I felt it was more of an LM problem than an obstruction problem (LM~1.0 in the clouds, averaging 6.7 elsewhere).  But with meteors coming at 10-25/minute, right after the peak, I decided it was best just to estimate it as obstruction. My attempts to get an "equivalent LM" seem to overcorrect the rates more than the obstruction estimate, so I'll stick with it.  It was cheerily back to F=1.0 in 30 minutes, anyway.   

> Second, I had taken the LM chart for Gemini out, but when I
> looked up and of course saw Jupiter in the middle of it, I
> wondered if it was possible to do a valid star count with a -2
> magnitude planet in the field.  (Relatedly, I wondered how many
> novices, just a little newer than I, might have used the Taurus
> star field and counted Saturn as a star.)

If I recall correctly, neither Jupiter nor Saturn were actually IN the IMO areas 4 or 8, although both were close.  Of course, if either were in the field, there would be the danger of them overwhelming faint stars.  

I'll leave your radiant question for others.

Whatever the ZHRs, it WAS a great show, and that is the most important thing.

--
Wes
http://skytour.homestead.com



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