as a sct-newbie who has played mostly with refractors all my life, I am asking more experienced colleagues for advice. I decided to experiment a bit with larger apertures and bought the 8 '' Meade LX200 ACF. The telescope is almost new, originally bought in the store in April this year. According to the previous owner, it has never even been cleaned, not to mention taking it apart or opening it.
I have had it for several days during which I am not able to get a satisfactory image quality. Perhaps it is a matter of special weather conditions and seeing - the image in my refractors has also been very poor lately. However, in such a situation, I started looking for possibilities to improve the image by improving the collimation.
And here I ran into a problem. If I collimate a telescope on a star, obtaining a regular, even ring of a defocused image, the collimation assessment method already mentioned here on the forum and described here: http://www.robincasa...ro/collimation/ shows considerable deviations from the norm. Having positioned myself so that I can see the shadow of the central obstruction is more or less centered around it, the outer rings proof to be not only non-centric, but not even circular. When I was drawing the image below from the photo, I discovered that the outer ring was in the shape of an ellipse.
Conversely, when I look at these rings from the outside, I position the secondary to make them more or less centered, and then make a star-test, the ring becomes slightly uneven in the defocused image.
What do you think about this situation? Does this mean that some elements such as the corrector plate or the primary mirror, are not mounted centrally?
Edited by LukaszLu, 02 November 2021 - 12:43 PM.