I have had my ETX 90 Astro since the 90's when they came out.
When I first got it the object I was looking at would drift all the way out of the field of view.
I took the bottom plate off and opened up the screw holes in the motor. I was able to get it to track after just a couple seconds which is good but I have been bothered by the Alt Sticking on it. If I loosened the dec lock it would take a little force to get the tube to move. This also made it impossible to finely move the tube.
I finally said the heck with it and removed the tube from the mount, I then took the setting circles off and lubed the bushings with Synthetic Polyolefin (PAO) Lube.
It is made with Plastic on Plastic, and Plastic on Metal surfaces. It is now Amazingly Slick smooth. This grease also does not get thick in the cold, and thin in the heat.
I use the setting circles on it and found the RA setting circle so I pulled it apart and re-Glued it slightly looser and lubed it also.
Meade used a light oil for lube but this is so much Superior it isn't funny! I also re-lubed the mirror baffle, the mirror shift is now 100% GONE!
I found a Dew Shield that is like a Questar, put a RA finder on it and electronic focuser. A Premium Solar Filter has made it a very fine White light Solar Scope.. The 90mm really cuts through the bubbly daytime seeing.
It is amazing what you can see with these little scopes, with a bit of work they can be much more user friendly..
BTW you can get this stuff on EbAy cheap enough.
Sticking ETX 90 Astro Dec and RA Circle
1 reply to this topic
Posted 16 August 2013 - 09:34 PM
I'm the proud new owner of an old ETX 90RA... I've had it less than a week now. I had to put a little work into it (fix RA drive gear, secondary baffle fix, tighten corrector cell) but for 75 bucks I scored. What a great little scope!