Quote:
Originally Posted by Terry B
Peter.
I'm not sure how the donut on the primary could be the cause of the halos.
The donus should not get any light on it unless you have off axis light hitting the mirror. The secondary should shaddow the centre of the mirror completely.
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I have assumed he's talking about a Newtonian and you're right, assuming the thing is reasonably well set up. But Murphy's law is alive and well and I prefer to solve problems 'bottom-up' so to speak and collimation seems to me the thing you would check first.
Peter