Focus. Knob is tight - Meade ETX-125EC (500 x 127mm) Telescope
Remove the OTA from the rear cell; unscrew the focuser shaft
about half way (CCW) and remove the knob or electric focuser unit; there
are three very small hex cap screws which hold the OTA into the rear
cell; remove these and save in a tuna can or similar, because they WILL
get lost if you place on the countertop.
Once done, merely grasp the blue OTA in one hand with a rubber glove for
grip and the rear cell/fork arms in the other hand and pull gently
apart....do NOT twist while separating!
You will see where the threaded focus rod inserts into the
OTA....typically binding is causing the shifting, but most of this is
due to poor milling by Meade on some 125 models. You can improve these
imperfect models greatly, but do not expect to eliminate all focus
shift. Run the focus rod gently all the way CCW until you feel
pressure...do NOT force or you will damage. Once there apply a thick
grease, such as pure white Lithium (available in the tool dept. at
Lowes) in a very thin layer, pushing hard into the threads...do NOT
apply too much or you risk getting this stuff on the optics eventually.
Once done, put the knob on the rod temporarily and run it in and out all
the way slowly about 3-4 times. Once done, run it HALF-WAY between all
the way and all the way out and stop. At that position, turn the OTA to
about a 45-degree tilt, with corrector down and put 1-2 DROPS of 3-in-1
oil right where the threaded rod goes into the threaded rear cell of the
scope and QUICKLY run the focuser CLOCKWISE to get that thin bit of oil
into the rear cell threads.
Once done, run the threaded rod slowly all the way CW and then CCW about
2 more times.
This procedure will greatly improve the performance....NOTE: do NOT put
more than 2 drops of oil on the rod! Read More At : ETX-125EC (500 x 127mm) Telescope...