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Advice/opinions
Hello All,
This is an image I took a few nights ago. Don't worry about the overall quality - apart from the focus issue I'm actually fairly happy with the basics of it and I haven't processed it much.
What I am concerned with is the coma/distorted stars especially around the edges.
Its taken with an c9.25 f/10 and the first time I have used a new centralds cooled 60D. I don't think it's a camera issue - I have used a 40D and a 550D previously and I have never seen this before. Also it's not my initial focusing - also done the same way as many times previously.
I suspect it may be caused by my dew heater? It was a fairly cold night and I may have had the heater a bit high and may not have waited long enough for the temperature to stabilise? I took 3 other images that night - 1 of them showed the problem a little bit the other 2 were "normal". Maybe if the dew heater is too high it can cause a temperature gradient across the corrector plate and cause the image to distort? Or as it heated it change the focal length slightly (and changed the focal point)?
Does anyone have any other ideas or is my theory likely to be correct?
Regards,
Tony.
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