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Re: HELP! CAN'T GET FOCUS

Started by Alex McConahay, 12/25/2004 09:34AM
Posted 12/25/2004 09:34AM Opening Post
Jon,

Is the problem that you are getting sharper and sharper and it stops before it gets sharp or is it that you get it sharper and sharper then it becomes softer and softer without ever getting sharp in between?

Alex
Posted 12/25/2004 05:50PM #1
The issue could be any one of a number of things--but what is interesting is that you can focus indoors pointing out. This would indicate to me that you can focus when you are at a stable temperature--but when you take it outside, you have some thermal currents spoiling your view. Is the image steady or does it seem to move? If it moves, suspect temperature differentials. TO cure it, take the scope outside, and leave it there for an hour, then try to focus it.

If it does not work well after it has been outside for a while, then pick a lmedium bright star, and bring it to as close a focus as you can. Then take it in and out of focus. The image should have a circular fuzzball around it. If it is not circular, you have a collimation problem. Collimate your scope. (Do this with and without your diagonal, and see what you can get.) The circles should be round in either case.

If it still does not work, check you optical path for things like dirt, dew, and such.

Oh, and I am assuming you are not simply overpowering your scope.

Of course, then we go back to--why is it sharp inside the house, and not outside.

Alex
Posted 12/25/2004 07:25PM #2
How long have you had the scope?

How long are you waiting for it to cool.

In general, looking through a window should cause the image to degrade significantly, especially at higher magnifiations...

jon