RE: [APML] Mewlon 250

["Gene Horr" <genehorr@houston.rr.com>]

-----Original Message-----
From: astro-photo-bounces@seds.org
[mailto:astro-photo-bounces@seds.org]On Behalf Of Radu Corlan
Sent: Monday, June 02, 2003 7:20 PM
To: Discussion of Film Astrophotography
Subject: Re: [APML] Mewlon 250

On Mon, 2 Jun 2003, Frank Barrett wrote:

>> I'm starting to understand (and hit) the limits of my C8 and am starting
>> to consider what my next scope should be (drooling really<g>).  What I
>> want is an RC, but that's kinda outta reach right now.  I've read great
>> reviews and I'm considering a Mewlon 250 for the following reasons:

> The Mewlon is a Dall-Kirkham - which has even more coma than the sct.

Ah, nope.  In fact the star images are far better than _any_ of the non
RC Cassegrain variants within most of the field.  Only at the edges do
the stars get as bad (but not worse) than a SCT.  What's even better 
about this design is that the coma is very easily corrected.  The
downside of the corrector/reducer is that it does introduce noticeable 
vignetting across a 35mm frame.  There is a f/6 reducer/corrector in
the works but it is most likely only for CCD work.

The advantage of the R-C design is that it can be made "faster" and that
the stars are even across the field which makes it a great tool for 
scientific measurements.  Also most designs have much less field curvature
than other production Cassegrain variants.

All in all I would not recommend the M250 for emulsion imaging, but 
optical quality has nothing to do with it.  It is an outstanding CCD 
platform.  The main problem with film is the system's "speed".

I'll try and do some test shots for you.

Gene Horr
genehorr@houston.rr.com








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