Thanks everyone
Joe - I will indeed, and Ganymede's high on the list
Quote:
Originally Posted by blinky
okl, interesting. I'd be interested to know what its from when you work it out. Have you tried collimating with a false star? I read in an astronomy mag recently its possible to pin prick a hole in foil and put a bright light behind it to use as a false star. yet to try it myself.
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Collimation for me I think is just a case of practice - it's the first time I've owned an SCT, and so I'm learning about adjustments mainly by stars inside/outside/close to focus. I made a Duncan Mask but it's hard to use when collimation is nearly there (it's good when it's far out). As I set up and take down each session, I need to have a fairly rapid method of collimating or checking collimation - the light/foil is possible, but I'm usually hoping to have stars handy
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The rind effect - I read a very
interesting article by Martin Lewis, essentially a mini research project on what might cause edge artefacts on Mars. The associated
Cloudy Nights thread also has some more good discussions. There's a good bit of info to digest, whether or not it all perfect! I'm a little more convinced that it's a lot to do with diffraction at hard edges, and at least after last night, convinced it's not primarily focus, collimation or wavelets, though I imagine errors in these would not help.