I recently completed work on a 10" dob.
I have been using it (mainly for testing purposes initially) and have noticed a coma that I just can't get rid of, no matter what I do collimation-wise.
So - tonight, just for the heck of it, I recalculated where the centre of the focuser hole should be (43.75") and where I actually drilled it (44.50").
http://www.cloudynights.com/ubbthrea...reheadslap.gif
Before I go and re-drill another hole - is the additional 3/4" that I drilled in error likely to be a cause of my coma probs? Viewing stars thru the scope, they all appear to have "tails" at about 270º
Would be much obliged for any help on this!
http://www.cloudynights.com/ubbthrea...emlins/bow.gif