Celestron 80ED: How to shorten focus distance?Posted By Timothy Iafolla |
Hi all,
I recently bought a Celestron 80ED "spotting scope", which is similar to the Orion ED80 (same optics), but with a smaller tube and a R&P instead of Crayford focuser (and an erecting 45 degree diagonal). All was well at first: I replaced the erecting diagonal with a 1.25" standard diagonal, no problem. Then I replaced the 1.25" with a 2" Williams Optics diagonal, and found that I don't have enough forward travel to bring it to focus. Also, a Stellarview binocular viewer will just barely make it, if I use the internal Barlow lens and the 1.25" diagonal.
So right now the scope doesn't work with my best 2" eyepieces or the binoviewer using anything over 10mm eyepieces (20mm plus the internal Barlow).
My question is, of course, is there any way to fix this? Unfortunately the mirror cell and focuser assembly are both threaded directly onto the optical tube, so I can't just shorten the tube without some way of re-threading the tube end. I've thought of cutting a section out of the middle of the tube and splicing the ends with a sleeve. But this would bring the rear baffle closer to the objective, which would (maybe) cause vignetting. Any suggestions?
Another qustion: am I having this problem because it's really a spotting scope? IOW, does the Orion ED80 have the same problem? If not, I can sell this one and buy an Orion scope.
Thanks,
Tim Iafolla
I recently bought a Celestron 80ED "spotting scope", which is similar to the Orion ED80 (same optics), but with a smaller tube and a R&P instead of Crayford focuser (and an erecting 45 degree diagonal). All was well at first: I replaced the erecting diagonal with a 1.25" standard diagonal, no problem. Then I replaced the 1.25" with a 2" Williams Optics diagonal, and found that I don't have enough forward travel to bring it to focus. Also, a Stellarview binocular viewer will just barely make it, if I use the internal Barlow lens and the 1.25" diagonal.
So right now the scope doesn't work with my best 2" eyepieces or the binoviewer using anything over 10mm eyepieces (20mm plus the internal Barlow).
My question is, of course, is there any way to fix this? Unfortunately the mirror cell and focuser assembly are both threaded directly onto the optical tube, so I can't just shorten the tube without some way of re-threading the tube end. I've thought of cutting a section out of the middle of the tube and splicing the ends with a sleeve. But this would bring the rear baffle closer to the objective, which would (maybe) cause vignetting. Any suggestions?
Another qustion: am I having this problem because it's really a spotting scope? IOW, does the Orion ED80 have the same problem? If not, I can sell this one and buy an Orion scope.
Thanks,
Tim Iafolla