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Re: (meteorobs) Limiting Magnitude

Lew,
  Actually, I thought I'd wind up putting my foot much farther down my throat
than I must have in my reply to Asaf!  I do indeed recall reading that star
counts should come from at or near zenith, but let disinformation from another
source overide what was only a vague recall.
   The truth is, I'd rather use zenithal areas only for the exact reasons you
state...the ease in counting. Besides, if I can count areas at and near zenith, I
come up with higher LM's, which gives me a small motivational boost to get out
there and observe.  And I'm certainly glad you "called" me on it, else I would
have continued counting stars on the horizon!
   But I must admit that haven't always counted three fields like I should.
During my first year out, I simply have not wanted the "work" to spoil the
"enjoyment," knowing that in time I'd be more familiar with all the (usable)
fields and their star patterns.
Kim Youmans

Lew Gramer wrote:

> Kim Youmans posted a great reply to Asaf's questions on Limiting Magnitude.
> As Kim says, recording frequent LMs is one of the things which distinguishes
> a scientific amateur meteor observer from someone "just watching" - without
> the LM (and probably at least magnitude estimates for the meteors you see),
> people will have great difficulty making any scientific use of what you saw.
>
> Your logs won't necessarily be "USELESS"! But the work needed to render your
> observation comparable to those of other observers around the world, and the
> inherent errors introduced by this kind of "compensation after the fact",
> make it really FAR less likely that you'll make a major contribution...
>
> One gnit to gpick on Kim's reply, where he wrote:
>
> >A good observer will count at least three of these regions, one near zenith,
> >one at about 40-60 degrees up, and one near the horizon to get a much better
> >idea what his/her total LM really is.  After all, meteors appear in any part
> >of the sky, right? ...
>
> Actually, Kim this is exactly what I assumed when I started out - but is not
> what the IMO recommends... Reading carefully over the IMO page on LMs at:
>
>     http://www.imodot net/visual/major01.html#sec52
>
> note that they define Limiting Magnitude as "the magnitude of the faintest
> star *near the zenith* that the observer can detect using slightly averted
> naked eye". And later on, they explicitly state that "The [LM star] fields
> should have an elevation of more than 40o".
>
> So in practice, for my own half-hourly LM star counts, I try to use the two
> (or three) LM fields which are closest to the Zenith, and that DON'T require
> me to move my body or crane my neck at all to count them. That latter item
> is key: I've often noted that even craning my neck 30 degrees can really
> reduce star counts due to distraction and lack of bloodflow to my eyes (or
> brain??), and can even cause what I call "strobing" - where brighter areas
> of my peripheral vision seem to "blink" brighter and fainter very rapidly.
>
> [Does anyone else experience this "strobing", especially when fatigued?]
>
> Clear skies and comfortable star counts everybody!
> Lew
>
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