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Collimating question
Hi,
I have a 250 mm reflector on a Dobs mount. It's been in the cupboard for a while and have decided to check the collimation. I have used a home made sight tube and seem to have it close - except: when I focus the eyepiece inwards towards focus I get the concentric rings around a star. These get closer and closer together then at the point of focus I get a flare. I have been using Rigel as a target star and have found that at 250 x mag. the flare makes it hard to see the small Rigel B star. Also on the other side of focus, I don't get the concentric circles appearing again - this is what makes me think that something is out of alignment.
Any ideas, thanks
Ross
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