RE: [APML] Question Regarding Astrophotography withTakahashiMewlon180

["Serge Theberge" <serge.theberge@wti.on.ca>]

Hi Gene,

The Mewlon 250 sure would fit the bill perfectly.  However, at $5000US for a
used one, that's over my budget (my wife insists that the kitchen renovation
has higher priority!).

There is a used C11 OTA on Astromart.com that comes with a JMI motofocus
w/digital focus counter.  Would that give me significantly better planetary
picture quality than my C8?

Serge

-----Original Message-----
From: astro-photo-bounces@seds.org [mailto:astro-photo-bounces@seds.org] On
Behalf Of Gene Horr
Sent: Tuesday, December 09, 2003 12:53 PM
To: Discussion of Film Astrophotography
Subject: RE: [APML] Question Regarding Astrophotography with
TakahashiMewlon180


> However, I also want to do planetary photography which right now I am
doing
> with my old C8.  I was wondering if I would get significantly better 
> planetary images by upgrading to a C11 OTA, the Takahashi Mewlon 180, 
> or something else altogether which would work well on my G11 mount 
> (and not have to mortgage my house to purchase).

The best choice would be a Mewlon 250.  But that is around 3X the cost of
the used M180.  The advantage of the M250 is the fixed optics in addition to
the high quality.

Read Thierry Legault's web page dealing with critical collimation and
planetary imaging.  With any of the moving primary Cassegrains (which
includes the Mewlons smaller than 250cm) the collimation necessary for good
planetary imaging is a moving target.  You have the potential for somewhat
better images with the M180 over the C8, but it won't be _that_ much better
assuming that both are critically collimated.  I would put my money into a
good bolt-on focuser like the Van Slyke for the C-8 rather than buying the
M180.  Or get a nice 4" APO.

Visually, though, you should see an improvement over the C-8 with the M180
in contrast.  The Mewlons are outstanding visual instruments.

Gene Horr
genehorr@houston.rr.com



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