(IAAC) Re: limiting mag. and personal equation (long)

Steve Coe wrote:
>So, maybe what I am saying here is that I need to add some more info to my
>observing form that provides some data about my state while observing. Is it
>late at night, am I sleepy?  Have I just had a snack and is my blood sugar
>spiking?  Have I just gotten up from a nap and am ready to go?  Is the
>combination of night, observer and object at its best, so that I am seeing all
>there is to see?  That is certainly tough to measure, but it might prove
>interresting, once you had gathered enough observations to generalize about
>your personal equation versus the "Faint Fuzzies".

Steve, actually the interesting thing is that all those factors you describe
SHOULD be reflected in changing Limiting Magnitudes throughout the night: they
certainly are in unaided-eye LMs, as evidenced by many a fatigued all-night
meteor session by yours truly under apparently unchanging sky conditions.

This is why I believe it might be key to try to correlate unaided-eye LM,
telescopic LM, and this new (for me) concept mentioned by Brian Skiff of
"surface brightness LM" together...

I was surprised by Jeff Medkeff's dataset, which essentialy showed large
differences between individuals' unaided LMs, even while telescopic LMs
for those same individuals appeared to stay inside a vary narrow range.

Jeff, your post went into detail on how you estimated telescopic LMs,
but you didn't mention how the estimates for unaided-eye LM were taken?
Were these also done by plotting stars in a predefined field, or was
some other method (e.g., IMO star counts) used?

If the LACK of correlation in Jeff's data were confirmed - which would
probably require other observations, particularly from observers adept
at estimating both telescopic and unaided LMs - then I'd have to wonder
whether telescopic and "surface brightness" LMs also correlate?

I think researching that correlation, particularly as and if it changes
with an individual's varying perception, would be tough... It would put
the "researcher" in the uncomfortable position of asking many observers
to perform TWO (probably difficult) LM estimates at the eyepiece, not
once but several times each night, under a wide range of sky conditions!

Come to think of it, though, using counts rather than plots to estimate
telescopic LMs - and generating a much larger number of potential count
fields around the sky - might go a long way to facilitate this tough but
fascinating data-gathering project!

How about it: anyone interested in co-designing such a study?

Lew Gramer

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