LX90 wedge

Combined reply to two postings below:

"Chris Taylor" wrote in message
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"Grimble Gromble" wrote in message
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"Chris Taylor" wrote in message
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It would have come out so much nicer with an equatorial wedge ;-)

Not forgotten. Things are extremely hectic at work at the moment so I
haven't bothered my boss with it again (he does actually do work which is
unusual for a director - in fact, if we come up with a suitable design,
he'll be doing most of the machining). When I broached the idea with him
first, a while ago now, he said, as predicted, "No, you don't want to do
it like that...". I think I mentioned that he decided he would want to be
able to make adjustments even though I was looking to avoid that and the
rather considerable extra cost.

I've come up with a very basic (but cunning) idea of how to approach the
mounting of the telescope on a wedge, and am contemplating a couple of
ideas regarding the adjustment. I'm a slow thinker but it's coming. Give
us a few more months...
Grim


No Probs, just having a dig. There'll be plenty of toys arriving during
the week to play with for a little while. Have you done a comparison with
an existing wedge? I've not seen one in the flesh yet. I'm over to the
States in about four weeks for Xmas and the new year and will probably
have a look around while there.

Thanks, Chris. I've seen pictures of the wedges for the LX90 and LX200.
Unfortunately, I don't think there's much to be learned from them.

The main stumbling block I have at the moment is more to do with nervousness
about securing the telescope to the tripod. It doesn't worry me so much as I
think it would trouble other users. The basic idea is to mount the telescope
on a triangular plate which would have a ball at one corner (to provide a
basic reference point), a cylinder at the second corner (to define an axis
in conjunction with the reference point) and just the plate at the third
corner (to define a plane in conjunction with the axis). This plate, with
attached telescope, would simply lift off the wedge which would have a
matching socket for the ball, a groove for the cylinder and a screw (for
adjustment? - see reply to Colin) to support the third corner of the plate.

What might trouble other users is that this will leave the telescope resting
on the wedge rather than being firmly attached to the wedge and thence to
the tripod. For myself, this wouldn't be a cause for concern as the weight
of the telescope is not inconsiderable and I suspect anything that might jar
the telescope and plate out of the wedge, might also knock over the tripod
anyway. It's just that if the worst happens, it will be easy for users to
point at the design and criticise that instead of whatever clobbered it.

Trouble is, providing secure(r) fixing points will add to the cost and I
don't want to do that unnecessarily. Perhaps when I've dealt with the wedge
itself in more detail, something will suggest itself. Perhaps some simple
clamps to secure the plate to the wedge, in case someone wants to use them,
will suffice? I've some simple ideas regarding that too.

"Colin Dawson" wrote in message
...
I've been thinking a little about your wedge idea. Something that you
should really consider is that adding the wedge to the tripod will reduce
the stability of the mount. In a nutshell, when I used to use my LX90 in
Alt Az mode, it was extremely stable a light breeze wouldn't effect the
scope, and any wobbles would dampen out is a couple of seconds. Since the
addition of the wedge, it takes ages (over 10 seconds) for wobbles to
dampen
out. It's more suseptable to light winds. Basically the wedge recudes
the
effectiveness of the original mount. Another problem, specific to the
LX90
is that I needed to attach an adapter plate to the OTA in order to fix the
scope to the wedge. The plate itself isn't a problem, in fact I highly
recommend them, as it does mean that the single bolt thread in the base of
the OTA is not getting worn down, and there's no threat of cross
threading.
The problem is that as the plate is in place, I can't use the scope in
Alt-Az mode without removing the plate (which I don't want to do)

It would be fantastic, if I could get a device that would allow me to
attach
me scope to the tripod in Alt-Az mode. What, I'm thinking of is a plate
that attachs to the the top of the tripod, using the existing bolt. Around
the edge a few (at least 5) pillars that suppose an upper ring/ platform.
The upper platform, will look similar to the part of the wedge that the
OTA
attaches to, complete with the holes necessary to bold the OTA to this
platform. Since this is something that wedge owners would want, you won't
need to supply the LX90 Wedge Adapter plate, or the bolts needed to attach
the OTA, as the owner's already got them. If it's engineered properly,
there's no reason why the scope shouldn't be as stable as if the OTA was
attached directly to the tripod. To open up the market more, you could
sell the adapeter plate and bolt set needed to upgrade an existing Alt-Az
mode into the raised configuration. (The marketing principal, is that it
stops thread wear on the base of the OTA).

Thanks for your comments too, Colin.

With regard to your own issues, I have considered the possibility of
splitting the wedge into 2 pieces. One piece would be a plate that would
bolt to the top of the tripod and on which the plate attached to the
telescope would rest in the absence of a wedge for use in alt-az mode. The
second piece would become the wedge itself and would then be inserted
between the telescope plate and the tripod plate for use in ra-dec mode.

This would introduce further work and expense into the project. However,
since the same interface would be used between the telescope plate/wedge as
between the wedge/tripod plate, there are some economies of scale to be made
here. Why the telescopes and tripods couldn't have been designed with this
in mind in the first place (thereby obviating the need for two plates as
well as a wedge) ...

Another advantage of doing it this way would be that any adjustment could be
incorporated into the tripod plate making the wedge and telescope plate
comparatively simple to manufacture.
Grim