Re: [APML] Can't Reach Prime Focus, What Are My Options?

["John Lanoue" <johnlanoue@hotmail.com>]

Hi Dave,

I had the same problem with my 4.5" f4.3 konus reflector.  With hacksaw and 
drill bits in hand, the problem was solved in about an hour.  I took off 
about 1.25" of the tube and redrilled the screw holes.  If you take off just 
enough, and no more, than you can reach prime focus at the bottom of your 
focuser's depth, and still use eyepieces at the top.

John



John Lanoue
Principal Software Engineer
Bedford, NH
http://www.geocities.com/johnlanoue/





>From: Dave Mueller <dmueller@bellatlantic.net>
>Reply-To: Discussion of Film Astrophotography <astro-photo@seds.org>
>To: Discussion of Film Astrophotography <astro-photo@seds.org>
>Subject: [APML] Can't Reach Prime Focus, What Are My Options?
>Date: Thu, 11 Sep 2003 11:01:07 -0400
>
>HI,
>
>I have a Discovery 8" f/7 PDHQ reflector with a 2" JMI focuser, and I'm 
>using a Nikon F3.  The JMI is 1.5" tall and won't allow the camera close 
>enough to the tube to reach focus (but it's really close).  I have the 
>Baader 2" T ring adapter, it only adds 10mm.
>
>So far, I've come up with the following:
>1) Relay lens
>2) New low profile focuser (like the Clement one, but at $400, it's half 
>what the scope cost!)
>3) Build a simple flange to replace the focuser and slide the 2" adapter 
>up/down to focus
>4) Re-do/replace the tube and move the secondary closer to the primary (and 
>maybe need a new secondary?)
>
>I realize a ready-made Newtonian isn't the best for prime focus work, but 
>it was the most bang for the buck (and works great with my ToUCam and home 
>made adapter).
>Is there some other option, like a 1.4x lens type tele-extender that would 
>provide a simple solution?
>
>Thanks,
>Dave
>
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