Quote:
Originally Posted by Camelopardalis
Naive question...what would one look for to tell the difference? Or is it a question of sitting them down side by side and comparing  |
Kind of. A much loved eyepiece under great sky will soon weed out the great from the ordinary, but those great skies don't come around too often (for me!)
Look for pinpoint stars in the centre of the field, in a fast Newtonian you may see coma at the edges, but that is expected, and check out the contrast in bright nebulae or on planets.
In addition, there are various tests that can be applied to add rigor both on the bench and under the stars - google 'star testing telescopes' for some examples of how to spot basic faults
Oh, and one thing. If you find that a mates mirror is a dud, unless asked, its polite not to mention it as some observers have quite poor eyesight
