In article <5cbf61$99b@hplvejl.lvld.hp.com>, noble@lvld.hp.com says...
>Bill Krosney (bkrosney@mbnet.mb.ca) wrote:

>: I'm looking at purchasing a 50mm Nikon lens for astrophotography.
>: I own a 55mm Micro-Nikkor (which is very nice), but at f/3.5 it's pretty
>: slow. I've come across two used 50mm f/2 Nikon lenses.

>The only way to tell if a lens will work for astrophotography is to try
>it. You might find that the 1.5 stops gained by going from a 55/3.5 to
>a 50/2 don't matter much. What matters is sharpness. That 55 might
>work better, and it might not.
>There are variations between lenses of the same type, even with Nikon.
>Stars are THE most demanding of subjects, and it's virtually impossible
>to relate lens performance on daylight photos to how it will perform on
>pinpoints of light at d=infinity (ie, stars). However, in one evening,
>you can take a roll of slides and evaluate several lenses. See if you
>can get the lenses on a trial basis, and check them out.

I agree with this - one night I took a bunch of different lenses
(Nikkor 35 f1.4, 35 f2, 50 f1.2, 50 f1.4, 50 f1.8 [compact], and 50
f1.8 [large version]) outside and shot (placed corner to diagonally
opposite corner) distant city lights, exposed to keep all but the
brightest lights near black. These lenses all perform differently
in the corners near infinity-focus with daylight subjects using wide
apertures, but point-light rendering quality near the corners of all
these lenses seemed dependent purely on FL and aperture (f2 and 35mm
FL gave smaller points [smaller coma "wings"] at the corners than f1.4
and/or 50mm FL). It was surprising... (I have not tried this with the
macro lenses, or slightly longer 85mm lenses [or with wider lenses...]).
Hope This Helps