On 28 Nov 2004 01:52:42 -0500, Allan Adler
wrote:


I would be more concerned if there was slop in the
drawtube/focuser body fit.

As a matter of fact, there seems to be, if I understand you correctly
to mean on the same surface that the rack is mounted to. It is mostly
near the rack but "slop" is a good description of it.

Ok. On some of the focusers, I don't know if Meade ever used it,
there are flat springs opposite the rack, and they furnish friction to
keep it from moving unless driven by the rack/pinion. If these are
properly set, they will hold the drawtube in a sort of balance with
the pressure of the rack, but will seem to be allowing movement, which
in use will not be the case. The old 6" Edmonds has two felt strips
opposite the rack, some have other methods, even going so far as to
having eliminated the rack for a friction drive, and having ball
bearings instead of springs or felt. The main thing is that with the
eyepiece installed, it should be centered and with the optical axis
also centered and parallel to the optical axis of the objective lens.
If it was a cheaper focuser, and has the felt, chances are that the
felt has compressed and is no longer holding it firmly. Quicky
repairs can be made by replacing the felt, but I prefer to use the
flocking from the film slit of a 35mm cartridge instead of felt. It
seems to not compress as quickly, and sometimes gives a little more
"solid" feel to the focuser.


When you say "to one side", I think you mean either towards or away
from the eyepiece.

It should be holding it so the shaft can't move up or down or towards
the drawtube easily. If it's too loose, it acts like backlash, or
excess play when changing the directon you're moving the drawtube.
There are as many variations in how it was accomplished as there are
makers of telescopes, every one of them believing they have a "better
idea." My own "better idea" would be a planetary drive fine focus
knob, but due to the costs of making such an animal, maybe it wouldn't
be worth it. I probably have ten or fifteen focusers in different
stages of "maybe this will work" in the basement, but still have to
come up with the "perfect" idea. It's pretty hard to improve on
something that people have been working on for several hundred years.