[APML]: Telephoto 200 -300 mm

[Michael Stecker <75232.2632@CompuServe.COM>]

     All this discussion about telephoto lenses on the APML has brought up an
old problem/question that I have never solved.  I would like to get a lens for a
35 mm camera in the 200 - 300 mm focal length range that will give good
astro-images without the use of filters.  I define a good astro image as one
that is relatively sharp with good contrast. Furthermore, and very important to
me, I would like the entire field to be evenly illuminated with no hot spots and
have round stars with no color  (blue halos) in the entire field of view.  So
far I have not found such a lens in these focal lengths.  I have tested the
Tamron SP LD 180 mm f/2.5, Tamron SP LD 300 mm f/2.8, Nikon ED 300 f/4 and Canon
"L" 300 mm f/4.  All these lenses gave unacceptable star images.  The most
common problem was "color" although coma and uneven illumination was a problem
in some as well.  Can anyone recommend a good 200 - 300 mm lens that will give
good astro-images as defined above?

                                                                                 
Michael Stecker
                                                                                 
75232.2632@compuserve.com
                                                                                 
Los Angeles, California