Have you ever heard of this term: "Tensioned primary mirror"?
I'm a beginner, so I don't rule out the term, but I don't understand how you can bend a piece of glass. It seems that my 8 'F4 Newtonian (bought used) cannot be used properly due to the tense primary mirror.
I understand the following: before I bought it, a person tightened the screws that support the mirror and then stored the telescope for a certain period, long enough for the mirror to twist and stay that way. If I did not understand well, please correct me.
But is this possible?
The effect is that the stars have a triangular shape, in about the same direction, not as a coma (from the inside to the outside). I've already checked for pinched optics, and I've even loosened the screws more than I would have liked. I'm attaching a picture taken by someone who knows these things better than I do.