To: atm{at}shore.net
From: Andy Saulietis 
Reply-To: Andy Saulietis 


Re folded refractor alinement..




>        I am making a folded light refractor and I am curious as how to
>make sure the objective is square to the first ( and only) reflective
>surface.  What visual confirmation am I looking for?  I don't want to
>make any collimating adjustments on the front objective  just on the
>mirror where it is folded.

I just completed a 6"f8 folded apo, to make it fit into an existing
fork mount for my CCD camera.

One way to get the folding mirrors alined is to put the OTA vertical, put a
piece of glass over the cell, and place a cross-hair finder scope (focused
at
infinity) down over the glass. Then put a low x eyepiece in the main scope,
you should see an image of the finder's crosshairs. Illuminating the finder
eyepiece will help in finding the image. Adjust one or both folding mirrors
to center the reticle in the field of view. The accuracy of this depends on
how square the 2 lens cells are with the optical axis of the lenses.

Alternatively, you can use a laser collimator placed on the glass instead
of the finder, also pointed down,. This assumes the collimator's tube edge
is square with the beam. Put a piece of ground glass or wax paper over the
focuser & center the laser spot in the eyepiece holder. Do NOT use an
eyepiece with this method..;)






Andy Saulietis
ISS Enterprises
PO Box 19
Mayhill NM 88339


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