Re: [APML] OAG for 2.7" focuser

[Matt BenDaniel <matt@starmatt.com>]

Chuck Vaughn wrote:
> 
> Matt,
> 
> >> There's a bigger problem. The Pentax 6x7 cannot be used with an OAG
> >> because the spacing between the FF and the film will be wrong.
> >
> > Why?  If the OAG is in front of the FF, the FF/film spacing is
> > maintained.
> 
> The prism is after the FF. I made it this way because the off axis
> stars are comatic. It made a big difference in the ability of the ST-4
> to see faint stars. Guide star selection is as easy as with a separate
> guide scope.

Chuck,

One additional point...  Roland designed the new Traveler FF to have its
rear element exceedingly close to the Pentax 67 body.  There is no room
there for pickoff.  The only way to pickoff behind that FF is to put the
prism inside the camera body, as Gene has been discussing.  In that
configuration, I wonder if the prism is so close to the film that its
umbra really does hit the film, which would mean total information loss
in that region.
-- 
Matt BenDaniel
http://starmatt.com

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