Re: [APML]: Surface brightness

[Jerry Lodriguss <jml@astropix.com>]

>Since photographically speaking, we are interested in the objects  
>surface brightness for selection of film, meeting concerns over reciprocity 
>failure and guessing the exposure time, the "Grail" in this case is to be
able to 
>derive the optimum film and  exposure time for a given object and express 
>this in a mathematical formalism.



It would seem that this will be a very difficult task for most extended
objects as their surface brightness varies, somtimes quite irregularly,
especially for nebulae.  So really, there is no one perfect exposure time
for these objects. If you want the faintest stuff, you expose to the sky
fog limit at the darkest site you can find.

Jerry