Useful web page

[Sam]

Found this on the skywatcher website, it shows pictures of different star test scenarious for various problems - might be useful.

SKY-WATCHER TELESCOPE

Sam

[Astronut]

Thanks for that. There are alot of star testing sites but this is the first one I've read that mentions an astigmatic view can be caused by a secondary that is not perfectly flat. I've recently become worried that my secondary might be a bit dodgy but it's unconfirmed - it could just be bad 'seeing'.

[Sam]

I thought it might be useful for me to check the optics on both the 8" and the 16" - mainly for checking that I've got the collimation sorted but also to see if there's any trouble with the secondary on the 16" - given there's been a bit of discussion about that lately.

[ashenlight]

Great find Sam, I've bookmarked it. Cheers

Amanda

[ringz]

This site is good as well though it's primarily for SCT scopes

Thierry Legault - The collimation

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Martyn

[Doc]

Good find Sam.

I still think most of my problems lie from coma. To my untrained eye some of my stars have little comets coming of them. This only occurs towards the last third of the FOV.

Looking at this explanation it seems it's more to do with coma then collimation.

So until I can try different eyepieces or a coma corrector I'll live with it.