Quote: A Ronchi test comes out OK but I don't think the Ronchi image will reveal astigmatism (is that correct?).
-DannyMy warehouseMy Channel
Where should I be looking for the problem? I checked the retention of the mirror, not squished anywhere I can see.
I thought about it being in the secondary mirror.
I could remount it out of its current plastic holder (holds it pretty tight) but it would take some work.
Quote:Jon, thanks for the info, I thought it might be a known problem, hence my posting. I had suspected the pinching secondary, I think I will cut off the sides of the holder and silicone the mirror back on.Tom
Quote:...remove the cell from the telescope, turn the mirror 45 degrees, then replace and re-collimate... If the orientation of the ellipses turned with the mirror, the primary mirror is defective. If it does not rotate with the mirror, it can only be the diagonal. Taras
20" homebuilt truss dob 6" watson refractor