Re: quick note on Arne's picture of M31

[<aah@nofs.navy.mil>]

So, Michael thinks we only get to V=17 on a 100-minute
exposure, huh?  Terrible for a 4-inch refractor!
  As Michael states, the psf of the images is
not great (3-4pixels fwhm), which will improve once I
get ARNE polar-aligned and focussed.  I'm expecting a
hard limit closer to V=18 in uncrowded fields.  You would
rarely use the Mark IV for such observations, but it is
kinda fun to go deep once in a while.  One could, in fact,
look for very faint variables in 5 or 6 patches per night
in the sky with such deep techniques.
Arne