Project LX90 equatorial wedge - progress report

Have just sent a drawing,with explanation, to Simon Miller who kindly agreed
to have a look at what I've come up with so far. If anyone else would like
to review it, could you send me your email address (you can reply to me
directly)?

Alternatively, I could post it here with the drawing (jpg) attached, but am
unsure how this would be received by the members of the newsgroup (wouldn't
want to **** anyone off). The jpg is only about 48KB, but if you've got a
slow connection, and you aren't interested, it would just be a pain.

As ever, any comments and suggestions would be gratefully received.
Grimble

Grimble Gromble wrote:
Have just sent a drawing,with explanation, to Simon Miller who kindly
agreed to have a look at what I've come up with so far. If anyone
else would like to review it, could you send me your email address
(you can reply to me directly)?

Alternatively, I could post it here with the drawing (jpg) attached,
but am unsure how this would be received by the members of the
newsgroup (wouldn't want to **** anyone off). The jpg is only about
48KB, but if you've got a slow connection, and you aren't interested,
it would just be a pain.

The newsgroup news:alt.binaries.pictures.astro is specifically for the
posting of photos images and drawings. There are some wonderful
astro photos posted there - easily the equal to the splendour of the
professional ones. If you can't get that group because of censorship
by your ISP, try www.MySky.org/ which robotically collects stuff posted
there and (I think) can receive posts for onward forwarding to the NG.

HTH

--
Graham W http://www.gcw.org.uk/ PGM-FI page updated, Graphics Tutorial
WIMBORNE http://www.wessex-astro-society.freeserve.co.uk/ Wessex
Dorset UK Astro Society's Web pages, Info, Meeting Dates, Sites & Maps
Change 'news' to 'sewn' in my Reply address to avoid my spam filter.

"Grimble Gromble" wrote in message
...
Alternatively, I could post it here with the drawing (jpg) attached, but
am unsure how this would be received by the members of the newsgroup
(wouldn't want to **** anyone off). The jpg is only about 48KB, but if
you've got a slow connection, and you aren't interested, it would just be
a pain.


Hi Grim

Couldn't find this on the binaries NG. If you e-mail the pic to me I'll put
it on my webspace and post a TINYURL back to this thread.

Try

As it happens, Santa delivered a wedge to me while visiting the fossils for
Xmas as the supply-chain and costs were favorable (SIC) on that side of the
pond. Still keen to see the design though!

Best Regards


Chris

"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
============================================

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.
=============================================

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

"Chris Taylor" wrote in message
...
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?
The Meade wedge uses a hinge which I was trying to avoid because I'm not
convinced you can remove all the play from it. I imagine one can come pretty
close using metal in plastic and slight interference fits, but it's almost
completely outside my experience - certainly for something as heavy as a
telescope.

How are plates S and T secured to the scope and tripod?
One plate would have a hole through the middle and a screw to bolt it to the
telescope base, the other would have a nut fitted to it so the tripod could
be bolted to it. Once attached, there shouldn't be any need to remove the
plates so as long as they don't twist, there doesn't seem to be much to do
in this regard.

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?
The two plates comprising the wedge would be offset so that the centre of
gravity of the scope would still be (roughly) above the centre of the
tripod. The extra height would be detrimental to stability, but that happens
on the Meade wedge anyway. I have considered using concentric spheres which
would also obviate the need for a wedge altogether - and the Meade tripod,
since it could have its own support - but the machining involved is outside
the realm of what our machines at work are capable of, elegant though the
solution would be. There is still the possibility of using some sort of
gimbal mount. I'll sleep on it for a few months (I do my best thinking
asleep).

Thanks for sending the drawing, I now have a better understanding of the
concept.
You're welcome. Thank you for circulating it more widely. When I find time,
I'll try to get a sketch of the wedge arrangement sorted out. The plates
design doesn't affect that greatly.

Grim