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[OM] Re: 500/5.6 Rubinar / MTO Catadioptric lens

Subject: [OM] Re: 500/5.6 Rubinar / MTO Catadioptric lens
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxx>
Date: Thu, 22 Jun 2006 06:46:39 -0400
This is identical to the scope I have
<http://cgi.ebay.com/ORION-90MM-MAKSUTOV-SPOTTING-TELESCOPE-MAK-500-MM_W0QQitemZ7614373034QQcategoryZ74930QQcmdZViewItem#ebayphotohosting>
I think I said it was an Adorama scope but I was in error if I did. 
It's an Orion identical to what's pictured here.  However, when I bought 
it (used) it was configured only as a 500mm/5.6 camera lens with T 
mount.  Adorama used to sell what appeared to be the same optic and they 
also sold (still do) an adapter kit for telescope use which includes a 
45 degree erect image diagonal and a 25mm 1-1/4" Plossl eyepiece.
<http://www.adorama.com/PROSS500.html?searchinfo=spotting%20scope%20pro-optic&item_no=1>

As I reported earlier the lens suffers from low contrast which is 
probably a byproduct of the diffraction around the large secondary 
mirror needed to support the f/5.6 aperture.

Until this very moment I never thought about using PhotoShop to jazz up 
the contrast.  This lens/scope has been sitting on the shelf since well 
before I started doing digital stuff.  I'll have to give it a try.  If 
its only problem is contrast I may have something more useful than I 
thought.

Chuck Norcutt


Jeff Keller wrote:

> Hmmm ... I don't remember seeing any 500/5.6 lenses before I came across the
> MTO / Rubinar. It sounds like the back end of yours is much different. Does
> it have the heavily curved front meniscus lens of a Maksutov or the
> relatively flat front lens of a Schmidt-Cassegrain?
> 
> -jeff



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