RE: ATM ...on homebuilt EQ mounts

[<youngdh@erols.com>]

I made an ATM eq mount out of 2.5" pipe threads for my 6" F/7 Newt. It works
great and the mount is very sturdy. You need to lap the threads with lapping
compound. You can use automotive heavy duty rubbing compound to do this if
you don't have axis to a machine tool and die supply house. Put the paste on
the threads and screw on the mating end. Rotate the pieces back and forth
with the lapping compound in the threads. You will need to occassionaly
clean the dirty paste out and replace with fresh as it loads up. This will
polish the threads down. If there is casting flashing on the threads, you
may want to take a wire brush or Dremel tool with a wire buffing wheel to
get the flashing off quickly before lapping. Once this is done and the
surfaces rotate together smoothely, you'll need to use an anti-backlash
grease. This stuff is available, but, hard to find. I couldn't locate a
local source, so, I tried heavy duty bearing grease. This didn't give the
results I wanted. I had some silicon grease I got from Radio Shack (comes in
a gray tube). This worked great! I've been very pleased with my mount. There
is absolutely no vibration (that I can detect and that's what counts). I
tapped and threaded holes on the RA and Dec rotational axes to thread thumb
screws in to use as brakes and/or to lock the Dec axis while rotating along
the RA axis.

Pipe fittings are an inexpensive way to make a GEM. Granted, you don't have
setting circles, but, you can fit Digital Setting Circles and encoders on it
and have a more accurate means of pointing. This is assuming you don't want
to navigate the skies by starhopping.

Regards,

Don Young