Quote:
Originally Posted by Greggles
Thanks for the response. Yeah this is why I shouldnt be writing posts at almost midnight. I was meant to mention star testing as you have reminded me. When I defocus a bright star at high magnification the mirror seems to be pretty dead center. But all the photos online show multiple perfect concentric rings around the mirrors shadow. I dont get that on mine it looks more like A bubbling ball of gas :p
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If the seeing is alright and you only slightly/gradually defocus, you should hopefully see some tight concentric rings (albeit they may still be a bit wobbly), but the more you defocus, the rings will present just as a large greyish sphere, I've found. I'd be more concerned about the concentric secondary shadow, and it sounds like you've got that sorted. I may be wrong, but if the secondary is concentric with the star outline, then the appearance of rings is hopefully more an artifact of your seeing conditions and mirror cooling than your collimation.