Quote:
Originally Posted by gregbradley
That's great Paul. It sounds like you have great conditions. I know you are an expert in seeing from your planetary experience where its everything.
Of course guide errors are much smaller when using a short focal length. Longer focal length shows up errors much better. You see smaller guide errors with shorter focal length scopes.
I am not sure about this seeing measurement myself. FWHM seem to be a guide only. Good seeing is easily seen in the image given good focusing. I think that is one of the main criteria for measuring. FWHM values vary significantly in the same image on different stars. At least using CCDstack. So I don't know how anyone can come up with a FWHM number that is meaningful as it is more a variable than a fixed item.
Greg.
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Hi Greg,
You can always tell the nights of good seeing. The auto guider image doesn't jump about all over the place. I usually sit at the computer watching the guide errors to estimate the seeing. If they rarely go above 0.5, it's the best seeing I can remember, probably only happened once or twice, sometimes the maximum guide errors are about 1, but usually they go out to 1.5, which means I have about 3" p-p, what I expect from suburban Melbourne.
Cheers
Stuart