re: Thanks guys.
For Nick; if I see a similar effect again I'll use the other eye to see if that changes anything.
The temperature should not have been a problem but I was in a relatively lighted environment, small town with lights all over.
I'll have to take the scope to a darker place and see if the quality improves.
Is there any way to clean the mirror, without scratching it too much?
Thanks for the link Socrates ll