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

[George Anderson <georgea@cam.org>]

Hi Dave

The best bet would be to move the primary up in the tube. I have this
same setup with my newt, one location for visual and another for
photographic. You can have a small EP extender made up so that you can
leave the mirror in the photographic position.
Depending on how the primary cll is fastened to the tube it may mean
just drilling another set of holes or having a machine shop make up a
spacer to lift the cell the required distance.

George Anderson
Montreal Canada

Clear skies and good health

Dave Mueller wrote:
> 
> 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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