Some time ago, through the generosity of a coworker, I acquired an older Meade ETX90 that was in need of some work. The OTA was dismantled from the fork mount, the mount was missing some attachment hardware and the electronic controller was non-functional.
After a good cleanup and some TLC, I was able to determine that about the only thing really wrong with the whole shebang was that the hand paddle was no good. I found a brand new one on Ebay for under $25.
Since then I’ve gotten a ton of enjoyment out of the little scope. It’s been just dandy for lunar and planetary outreach as long as the wind isn’t blowing too hard, and it makes a great grab-and-go lunar explorer at home. It’s set up for equatorial tracking, and I’m not kidding when I say it can be aligned and up and running in under a minute. It’s not much of a deep sky tool, but it puts up perfect star images on the brighter stuff.
Anyone who has owned one of these can attest to the optical quality of the Mak/Cass design, but they can probably also attest to the shortcomings of the mounting system. Shakiness is a hallmark of these scopes, and it’s because of the flimsy construction in the RA base. There really isn’t much you can do about it. It’s built in and part of the design.
If there’s one area where the little scope that could, couldn’t, it’s in focusing it with the little hand knob on the back of the optical tube. Every time you touch it the scope wiggles like you just whacked it with a bat. Accurate focusing with that knob is at best a guess, and more often than not I didn’t guess right.
One day while browsing a favorite seller on Ebay, I came across an electric focuser for sale that would fit the scope. It was listed at $40, and I figured if it worked it would be money well spent. Man, was I right!
The ETX90 on the field tripod in equatorial mode;
There’s plenty of motor focusers available on Ebay if you need one;
The motor focuser installs easy enough; take off the knob, put on a spacer and the gear, and bolt on the motor. Plug the cable into one of the AUX ports and you’re done;
The little EC hand paddle already has the focuser adjustment knobs built in. It works like a charm;
This past week I finally got around to putting the motor focus on and getting the scope out under the stars to try it out. The improvement in the usability of the scope is hard to overstate. It is so nice to be able to push the buttons and home in on perfect focus without the scope moving. I was messing around with Alnitak, which some might be aware is a close binary system that can be a challenge to split. I laid a 3x barlow in under a 12mm eyepiece, which brought the setup up to 312x, and had no problem focusing the pair into view. It really is that good.
Here’s the moral of the story; if you’ve got an ETX that’s giving you fits while focusing, get the motor focuser. You won’t regret it.