Thread: Advice/opinions
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  #17  
Old 08-08-2014, 04:45 PM
Tony_ (Tony)
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Join Date: Oct 2011
Location: Melbourne, Australia
Posts: 465
I think there may be a combination of issues - but the main problem does seem to be focus. I don't usually have this problem. I focus on a star and then go to the object - but I don't usually check the first image too carefully. The first sub was already out of focus. Either the dew heater theory is the cause or maybe the focus (primary mirror) shifted during the final goto.
I've had a closer look at some of my earlier images and there actually is some coma but it is sharp and nothing like this. It usually doesn't bother me too much (but it might now I've noticed it in more detail)
When I checked the focus after about 1 hour the bahtinov spike had moved quite a lot - more than I have ever seen before so there was definitely a change in focus.
I will take more care next time. I usually focus in the center of the image - is it better to focus off center?
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