Quote:To me it looks like the lines are slightly bowed inward, indicating a small amount of correction (i.e. slightly flatter towards the outer part of the mirror as a paraboloid would be). Whether this is a good thing or not would depend on the f-ratio. It may be easier to see the curvature if you adjust the screen to show only 3 lines.
The edge of the mirror looks a little bit suspect--there may be a narrow turned edge. Again, 3 lines would help to show this and a larger image scale would also help.
Homemade 'scopes 8"f/7,6" f/5", 6"f/4, 4.25" Schiefspiegler,60mm Coronagraph,60mm H-alpha system, 4.25" White-light Solar Newtonian,solar spectroscope, 4" f/12, 4.5" f/16 & 6" f/12 Schupmann Medial refractors, 4" Celestar, 19 Stellafane awards 9 in optics Engineering = Taking what you have and making what you need.
NW Mass, inches from Vermont
(well....it used to say that.....)