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Craig Smith
sage
Reged: 05/22/06
Posts: 229
Loc: Utah
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I got my AT66 several months ago, but found it didn't have enough infocus for my 2" diagonal and Hyperion zoom. I finally got a 1.25 WO diagonal and took it out today and tonight. I can now focus with about 30mm of infocus to spare. Here are my initial experiences:
Day: at 50x the image seemed to start to get grainy. I know 60x is about the max for daytime use anyway due to heat waves, but I wouldn't think resolution should be the issue. The limited aperture certainly is apparent.
Night: at 50x the moon had green fringing at the top of the field and purple fringing at the bottom. Very vibrant thin lines. And I've never heard of green fringing. Is this normal? My previous WO 80EDII didn't have any noticeable CA.
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Celestron Nexstar 6SE
OPT 2" Dielectric SCT Diagonal
Baader Hyperion Zoom
Stellarvue F50 Finderscope
Telecovers Case
Astro-Tech AT66ED
William-Optics 1.25" Dielectric Diagonal
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David E
Post Laureate
Reged: 05/25/06
Posts: 3021
Loc: North Carolina
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Craig, with what you describe, my initial impression is that your diagonal might have a warped, misaligned, or pinched mirror. This would cause the outer zones in the field of view to be slightly out of focus, possibly resulting in the fringing you see. If you get a chance, try it with another 1.25" diagonal. I have a Stellarvue version of the 66 with the same optics as yours and when the Moon is in focus, even at high powers, I have to look hard to see any fringing. But out of focus the fringing is pretty obvious, green on one side of focus and purple on the other.
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David E
If you keep a stack of old Orion catalogs in your bathroom, you might be an astro-redneck.
Edited by David E (11/01/09 09:53 PM)
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Craig Smith
sage
Reged: 05/22/06
Posts: 229
Loc: Utah
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Excellent thought, thanks. I just took it out with my Celestron prism diagonal as well as a 2" diagonal and fixed-length eyepiece. All combinations exhibit some color, but each combination was a little different. It was hard to do though as the moon is high and I just have it on a photo tripod, and the focuser won't hold the heavy combinations at that angle.
Anyway, some of this may be caused by the image not being sharp across the entire field. The difference in focus certainly is obvious. Now I know why people buy $300 eyepieces. Ugh.
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Celestron Nexstar 6SE
OPT 2" Dielectric SCT Diagonal
Baader Hyperion Zoom
Stellarvue F50 Finderscope
Telecovers Case
Astro-Tech AT66ED
William-Optics 1.25" Dielectric Diagonal
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Starlighter
Post Laureate
Reged: 08/03/07
Posts: 4494
Loc: Sunny California
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I own the WO 66mm which I believe is pretty much the same scope. Mine shows no false color on the moon. I'm using it with a WO 1.25" dielectric diagonal. The only false color I see that stands out is when viewing Vega and that's when I pump up the magnification or take it out of focus.
I suspect your diagonal has a problem since the AT66 seems to be a quality scope with lots of happy owners.
I love my little WO version.
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Celestron C4-R 102mm achromat
Celeston Nexstar 6SE SCT
Meade 80mm APO Triplet
Televue NP-101
Televue TV-85
Vixen A70Lf
Vixen A80Mf
William Optics 66mm Zenithstar Patriot
Celestron CG4 EQ mount
Orion Skyview Pro AZ mount
Vixen Portamount
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DLB242
professor emeritus
Reged: 07/29/08
Posts: 545
Loc: Pen Argyl, PA
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Quote:
Craig, with what you describe, my initial impression is that your diagonal might have a warped, misaligned, or pinched mirror. This would cause the outer zones in the field of view to be slightly out of focus, possibly resulting in the fringing you see. If you get a chance, try it with another 1.25" diagonal. I have a Stellarvue version of the 66 with the same optics as yours and when the Moon is in focus, even at high powers, I have to look hard to see any fringing. But out of focus the fringing is pretty obvious, green on one side of focus and purple on the other.
I had an AT66ED before I got my SV70ED and like David E. saw almost zero fringing in focus. I used a Stellarvue 1 1/4" diagonal with my AT66ED and a variety of eyepieces including a Barlowed TV 8-24 zoom. I suspect there is a problem with the diagonal also.
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David B
10" f/5 DOB
6" f/8 DOB
Celestron C8
Antares 1529 6" f/6.5 MoonLite Focuser
Orion ShortTube 130mm f/5 Reflector
Stellarvue SV102BV f/8.7 LOMO Doublet APO
Stellarvue SV90T f/7 Fluorite
Synta ShortTube 80
Stellarvue SV70ED
Edited by DLB242 (11/02/09 12:46 AM)
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Craig Smith
sage
Reged: 05/22/06
Posts: 229
Loc: Utah
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Thanks. Yes, I didn't expect to see so much color in an ED scope at only 50x. I'll check out the diagonal more. It would be easier to work with the mfg if both the scope and diagonal were either AT or WO, but this is all my dealer had available.
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Celestron Nexstar 6SE
OPT 2" Dielectric SCT Diagonal
Baader Hyperion Zoom
Stellarvue F50 Finderscope
Telecovers Case
Astro-Tech AT66ED
William-Optics 1.25" Dielectric Diagonal
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Craig Smith
sage
Reged: 05/22/06
Posts: 229
Loc: Utah
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The other issue may be that the diagonal is not sitting straight in the holder. That's the nice thing about the SCT diagonal, but it's just too heavy.
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Celestron Nexstar 6SE
OPT 2" Dielectric SCT Diagonal
Baader Hyperion Zoom
Stellarvue F50 Finderscope
Telecovers Case
Astro-Tech AT66ED
William-Optics 1.25" Dielectric Diagonal
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drago
member
Reged: 01/11/08
Posts: 95
Loc: Latvia
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2Craig:
how high above horizonte be moon, when you see fringing on this? maybe you see atmospheric dispersion?
try to see another time object was a minimum 35 - 40 degree above horizont, and check for fringing / ca.
as so, very good test imho is see to small constructions, i e approx 30 - 70 metres distant trees branch. try to look in telescope to a saurce of light ( i e streetlight) via btree branches. i compared with this methods one time syntas 70/700 achro and williams 66sd- difference is very good to see. on achro around a branches show a great amount of CA, on wo branches is clear...
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Sky-Watcher 100ed refractor on old HEQ5
Sky-Watcher 15075 refractor on EQ5 with motors
Orion Optics Europe 200 F6 newton
wo 66sd on modified synta AZ3
npz 8x50 seeker
18x50 beer bottle telescope
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