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Old 19-09-2006, 01:12 PM
Karls48 (Karl)
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Fast Newtonians and Imagining

Iím not happy. Last night I finally set up 150mm GSO Newtonian on pier I build in the back yard. GSO has not been used much because of hassles to set it up. I polar align it, point it on Jupiter and went to have a dinner. About hour later Jupiter was still in view of 9mm eyepiece. Beauty that will do me for now. I replaced eyepiece with GStar camera. I took 10 x 256 second exposure of Alpha Centauri. I had a look on the image and that when my problems started. The small stars were kind of V shape and some of them were almost 2 parallel lines. I replaced camera with the eyepiece; refocus telescope and stars appear OK. I defocused the image and there was small black spot on top of the defocused image. At this point I stopped to think logically and started fiddling with the collimation screws on the tube. I took few more images and they did not improve one bit. I had coffee and the smoke and decided that camera must be stuffed. I went home Meade ETS-105 and st it up with the Gstar camera and guess what, the images come out with perfectly, nice round stars. By 2 AM I took OTA home and have good look on it. And then it dawn on me. To reach the focus with GStar camera the focuser must be winded all the way in. That represents obstruction to the starlight 50 x 50mm. On 150mm mirror that is a lot and the obstruction is not in the centre. To my reasoning thatís why Iím having V shaped stars in the images.
I may be wrong, any comments and suggestion will be appreciated
Iím fitting Celestron 105 refractor on this mount to night. Aperture rules, well sometimes
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Old 19-09-2006, 01:19 PM
Karls48 (Karl)
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Sorry, I download it to wrong forum
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Old 19-09-2006, 01:26 PM
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janoskiss (Steve H)
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Sounds like you were seeing coma in your images. A camera or CCD normally sees a lot more sky than a typical eyepiece.

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Originally Posted by Karls48
Sorry, I download it to wrong forum
NP. Moved to Cameras & Photography.
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Old 19-09-2006, 02:30 PM
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EzyStyles (Eric)
I HATE COMA!

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Hi Karl, you might want to check out this thread:

http://www.iceinspace.com.au/forum/s...ad.php?t=13245
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