At 12:40 AM 11/21/98 -0800, you wrote:
>On another list, a question was asked regarding the best lenses to use on an
>OM-1 for astro photography. I replied Zuikos, of course, and went on to
>describe the merits of the 50 and 90 f/2 macros for wide field shots.
>Another list member replied with the following:
>
>"Never use a macro lens for astrophotography since they are flat field lens.
>While this is exactly what you want for macro photography it is exactly what
>you DON'T want for the stars."
>
>While I do not agree with this point of view, I thought I'd consult with
>this sage body before I make any response. I recall George making some
>critical evaluations in star tests and found these two to be quite good.
>Opinions???
>
>John P
>______________________________________
Actually, you DO WANT a flat field. Flat field means that there is no
distortion towards the edges, this is noted as 'kidney bean' shaped stars,
and referred to as coma. Generally 'fast' optical systems suffer the most
from this, and require complex designs, and multi-coated and special glass
optics to overcome the inherent problem.
One of my favorite lenses is not a Zuiko, but a Meade 12" f/10 'lens' with
a 3048mm focal length :) I actually do most of my astrophotography with a
f/6.3 focal-reducer / field-flattner which brings it down to an effective
1920mm focal length. Incorporated in the reducer is a built-in
field-flattner to correct for coma. This set up, however, produces a lot
of vignetting. I also have another system that operates with the same
scope at f/4.5, f/5.5, and f/11 with less vignetting, but the single lens
incorporated into this system does not do as good a job with coma.
As for use of Zuiko lenses for astrophotograpy, I use my 50mm f/1.8, and a
Vivitar 70-210 Zoom lense (both are MC lenses). MC lenses are good, APO
lenses are even better. I'd love to get my hands on a 350mm APO f/2.8 for
astrophotography.
Regards,
Danyal Medley
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