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Celestron ED80 focal length question

Started by tiafolla, 01/29/2006 08:25PM
Posted 01/29/2006 08:25PM | Edited 01/29/2006 08:26PM Opening Post
I just received Celestron's version of the ED80, which they call a spotting scope (in fact it comes with a 1.25 inch erecting prism). I can replace the erecting prism with a standard 1.25" mirror diagonal with no problem. If I use a 2" diagonal with a 2" eyepiece, I need to run the focuser almost to the limit of its inward travel to reach focus. And if I add a 1.25" adapter and EP to the 2" diagonal, I can't reach focus at all (even with a Barlow)...the optical path is just too long for the focuser to compensate.

So I have to do a lot of futzing around in order to switch between 2" and 1.25" EP's. Pretty seems like a scope having a 2" focuser should have enough in-travel to handle 2" accessories.

Couple of questions: is this also a problem with the Orion version of the scope? And, is there something I'm missing in the design of the scope that might help me out here? I'm ready to slice an inch or so off the main tube but wanted to ask before I do violence to the thing.

The good news is the optics are superb. On Saturn, I saw no image breakdown even with a 2.5mm EP, and stellar diffraction rings were close to perfect.


Tim Iafolla
Posted 01/29/2006 10:23PM #1
Hi Tim--
Are you using a low profile 2/1.25 adapter on your 2" diagonal? Also, are you near-sighted at all? I ask, because on my garden variety orion 100mm f/6 (which uses the same tube, I think, as the 80ed), I can only reach focus on my 1.25 naglers if I use a low profile adapter, which I have to borrow from the focusers on my newts. Also on certain 2" eps I can only reach focus if I leave my glasses on--there isn't enough in travel to compensate for my near-sightedness. Guess I'm interested in the same question...I've seriously contemplated shortening the tube, but it's a little scary.

George Golitzin