Last updated: 2 February 2008
Sent:	Wednesday, January 30, 2008 14:43:59
From:	Glenn Craig (
Shocked to hear about somebody in your old neighborhood helping
themselves to your 8"SCT. It is unfortunate that precision instruments
like that can be targets of opportunity for those who believe in getting
something for nothing, especially when nobody is looking.  I hate
thieves and their philosophy that what is yours is theirs, whenever they
can boost it without getting caught. 

Unlike physical objects which require time and energy to make and can
cost serious money to acquire, ideas are much more portable and only as
expensive as the effort you must take to understand them.

I have been thrashing away at the etx's vibration problem- especially at
higher magnification .  After going through about 9 or 10 schemes that
were not going to work, I finally hit on one that is like a step
backward, design-wise.  You can see in the picture that it is a brace
for the heavy front-end of my etx125. This design was no piece of cake,
as it had to be able to work in the space allowed, function with a
geometry that was capable of being changed easily, and I also didn't
want to attach it to the telescope in any way that it couldn't be
removed completely.  The answer for this is big 2" wide velcro strips. 
The brace was made with a variety of materials and went through several
design changes.  As this is still a prototype there are a lot of
features that could be brought out, like the ability to micro-adjust the
elevation.  As it is, you must loosen the wingnuts to use the
telescope's right-hand lock and autostar. It is possible to keep the
brace just tight enough to move the OTA up and down, but it isn't a very
accurate method.

But the thing actually works, and the tube becomes rock-steady when you
have it in position and tighten it. I can still bump the tube with my
hand, but even then the oscillations are dampened quickly.  Focusing the
telescope is completely different, as the normal forces of turning the
knob no longer cause the tube to shake.  The brace is one side of a
triangular support, that provides more stability than I thought it
might.  The only problem with the structure itself is the two wide
patches of velcro.  You have to really push and twist it in so that the
2 parts of the velcro form their temporary bond. Otherwise, the
structure is only as rigid as the floppy velcro end-points.  Perhaps
there is a better way to fasten these ends to the telescope, but I
cringe at the thought of epoxy or drilling holes or setting rivets. As
it is, once things are pressed firmly in place it works pretty well, but
is by no means the best solution.  This is a stage of its evolution.

I have noticed enough comments on 'the Mighty ETX' about this bouncing
problem that I offer this for your review and evaluation.  This idea is
still crude, but it could lead to something that is much better.

Thanks- Glenn


Go back to the Tech Tips page.

Go back to the ETX Home Page.

Copyright ©2008 Michael L. Weasner /
Submittal Copyright © 2008 by the Submitter