Quote:
Originally Posted by Robbos30
Is there anyway of testing your Newtonian mirror for its accuracy while it's still in your mirror box. Reason,:
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You can use a Ronchi eyepiece. 133lpi (or more). Fit the eyepiece, focus it up on any bright star. If the optics are f5 or slower and image displays parallel clean lines, (usually 4 to 6 lines focused), from edge to edge, then one can assume the optics are probably a 1/4 wave or better. If the system is faster than f5 you need to increase the sensitivity of the test by using a good 2x barlow in front of the eyepiece.