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tboss70
Carpal Tunnel
Reged: 11/25/05
Posts: 1973
Loc: Missouri
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Heat in my OTA always looked like a small "v" shape. The oblong shape is what concerns me. Still looks like astigmatism to me.
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Todd
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Midnight Dan
professor emeritus
Reged: 01/23/08
Posts: 558
Loc: Brockport, NY
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Brian:
Correct me if I'm wrong, but it looks like the image is elongated in one direction inside of focus, and elongated at about a 90 degree angle from the first image when outside of focus. Is that right?
If so, that is a symptom of astigmatism. You can try loosening all the screws on the secondary by the same small amount to see if there's too much pressure on the alignment screws. If that doesn't help, then it's a problem with the primary and there's not much you can do about it.
-Dan
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Scopes: Celestron NexStar 8, Orion EON 72mm ED/APO on Astroview mount (EQ3)
Eyepieces: Celestron 40mm, 25mm, Baader Hyperion 13mm, 8mm, 5mm
Other: Telrad, 2x Barlow, 0.63x Focal Reducer, Dew-not strips, DewBuster controller
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rmollise
Carpal Tunnel
Reged: 07/06/07
Posts: 1564
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Quote:
Brian:
Correct me if I'm wrong, but it looks like the image is elongated in one direction inside of focus, and elongated at about a 90 degree angle from the first image when outside of focus. Is that right?
If so, that is a symptom of astigmatism. You can try loosening all the screws on the secondary by the same small amount to see if there's too much pressure on the alignment screws. If that doesn't help, then it's a problem with the primary and there's not much you can do about it.
-Dan
Unless the screws are tightened insanely tight, it's unlikely loosening them will do squat. They are not pressing on the mirror but on a backing plate.
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Uncle Rod
Watch for Rod's New Book:
Choosing and Using the New CATs--coming soon!
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