[APML] Sky fog

[Alan Jones <ajones@apexsupply.com>]

Is there some emperical way to measure sky fog or is it just a subjective
thing that depends on what you like?.

Jerry says in his web site that sky fog is:
"defined as where the density recorded on the film from the natural skyglow
and any light pollution will start to overwhelm any density from the object
being recorded"
I guess my question concerns "overwhelm".  Is it possible to quantify the
term and measure it with some image processing software like PW or
Photoshop?  What I mean is, if I have a scanned image of a star and
background and I measure the star to be a certain count, is there a rule of
thumb that says that the background should be some percentage or less of the
star's count?  For example, if the background count is 30% or greater of the
star's count, then you've reached the sky fog limit at that site?  

Thanks,
Alan





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