Re: TUBE AND MOUNT DESIGN

Bob Luffel (bobl@gr.hp.com)
Mon, 10 Apr 95 10:15:39 MDT

> foucault test device or a reflected focused image of the sun on a
> wall) and the following "other" considerations:
>
> 10" od tube; focuser that has a racked in height of 2.5" and a
> drawtube travel of 2" (for example)
>
> tube wall thickness of 1/4"
>
> Calculate as follows:
>
> 1/2 the od or 5 inches Plus
>
> 2.5" for the focuser height Plus
>
> 1/2 the travel or 1"

1/2" of focal plane/focusser distance should be plenty. No need to extend it further unless photography is desired. This will permit the smallest diagonal size. I have found 1/2" is enough to get pretty much all eyepieces to focus (most eyepieces have a focal plane location outside the focusser, anyways).

Bob