"Grimble Gromble" wrote in message
...

Hi Grim

I've placed the drawing he

http://homepage.ntlworld.com/chris.t.../interface.jpg

The text summary you forwarded has been pasted he
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Forgetting the equatorial mount just for the moment, Plate S would be
permanently attached to the 'scope and plate T would be permanently attached
to the tripod, or some fixed pier. One of the spheres on plate S would then
mate with the conical trough in corner A of plate T to define a fixed point.

Another sphere would then mate with the channel in corner B of plate T to
define an axis and finally, the third sphere would rest on the plane in
corner C of plate T thereby fixing the orientation of plate S with respect
to plate T..

The channel and plane are designed to allow for changes in the distance
between the spheres as they are screwed in or out to alter the orientation
between plates S and T. The spheres would be fixed in place after adjustment
by the locking nuts (one or two of which could also be positioned under the
plate to allow for greater adjustment - ideally the distance between spheres
and plate S would be kept to a minimum).

The telescope (with plate S attached) could then easily be removed from, and
later repositioned in the exact same position with respect to, plate T. The
only problem at this stage is that there is no secure attachment between
plate S and plate T. This isn't necessarily a problem when using the
telescope in alt/az mode unless someone is paranoid about the assembly being
knocked. It does become an issue when one considers the next step which is
to create an equatorial wedge.

An equatorial wedge would be manufactured from a second pair of plates in
which plate T would be fixed (rigidly) at the relevant latitudinal angle
with respect to plate S. In this way, interposing the wedge between the
plates already attached to the telescope and the tripod would tilt the
telescope to the desired angle. Adjusting the spheres on the wedge would
allow the equatorial axis to be fine-tuned without affecting the set-up of
the alt-az interface so it would be easy to switch between the two modes as
required.

This is where I run into a problem that I'm unsure how to address, and that
is how to secure the interfaces. As I have designed them, the issue has been
reduced to one of clamping the spheres on plate S onto their respective
points a constant distance from plate T. It would be easy enough to use a
variation of a normal screw-on G clamp, and with nothing better suggesting
itself at the moment, I may go this route. It would, however, be nice to
find a more convenient way to carry out this clamping as telescopes can be
quite heavy and one doesn't want to be struggling with a telescope and a
clamp at the same time.
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My comments:

As the orientation adjustment is controlled only by point 'c' - Have you
considered placing some kind of a raised hinge between points A and B on
both plates. This would remove your concern regarding the secure attachment?

How are plates S and T secured to the scope and tripod? Also; when operating
in equatorial alignment, with the scope tilted, is it possible that the the
shift in center of gravity may impact on the overall stability of the tripod
and scope arrangement?

Thanks for sending the drawing, I now have a better understanding of the
concept.

Regards


Chris