Last Sunday night, the night before Labor Day, I took my ST80 out for another observing session behind my house. Like my previous night with the little scope, it was mounted on a MicroStar on Vanguard Auctus Plus 324AT tripod, which has a crank-up elevator column. Once again, a GLP was my only finder. Years ago I upgraded the focuser to a 2" GSO Crayford. And of course I took along my iPhone with SkySafari Pro and a camping stool.
Earlier that day, I removed the 2" GSO Crayford focuser. I needed to take off the little dovetail block that was screwed onto the OTA so I could have room to put the scope in rings and a longer dovetail. (I already had these, so nothing new to buy.) I also wanted to rotate the focuser to a different position. These changes would give me more control over how I position the OTA on a mount.
Now I have a longer adjustment range backward and forward, and I can rotate the OTA in the rings if needed. Many observers also say that having a scope in rings - rather than a dovetail attached directly to the OTA - will dampen vibrations. Probably true, but it does add to the total weight of the setup and can reduce the portability somewhat, since it can require a larger equipment bag.
Previously I had a Baader 1.25" RACI Prism Diagonal in the focuser. This time I went with an Olivon 2" RACI Prism. Of course, it would give me a natural orientation: not upside down, not reversed right to left. I intended to use the 2" diagonal with my 21 Ethos. I like to try these new setups inside the house before venturing outside.
Well, I tried it. Even with the ST80 in rings and longer dovetail, the 21 E was just too big and heavy for the little ST80. I had a longer dovetail I could have installed, but the one on the scope was just the right size. Also, I'd have to remove the focuser and rotate it on the OTA to get the focuser knobs out of the way of the longer dovetail. I didn't want to go there. Enough is enough. Besides, the 100 degrees AFOV of the 21 E would make the field curvature of the scope even more obvious.
So I opted for my Meade UWA 24mm instead. The Meade weighs about a third less than the 21 E, and is not as bulky. I had removed the bulbous shroud from the Meade UWA years ago. At that time I cut a ring out of the shroud to use as an eyecup.
The Meade worked out very well in the ST80. I did have to push the scope all the way forward on the dovetail in order for it to balance. This Meade UWA 24 eyepiece would give me 17x, 82 degrees AFOV, 4.7 degrees TFOV and a 4.8mm exit pupil. Not bad.
Edited by Sarkikos, 06 September 2016 - 08:32 AM.