I am looking at collimating my CPC 800. I have a ST-8300M camera, and I am trying to use the out of focus diffraction rings method to collimate my SCT. When I defocus the image, the resulting image gives a cut-off edge of the circles, like the attached photo. Any suggestions to what it could be?
Roof or wall of your observatory would be my first guess. If that's not it, how about you tell us what your setup is like - do you have an off-axis guider in the light path?
No. It’s not a camera artefact. I’ve taken everything out of the train so it’s straight through to the camera. I’ve taken the camera off and have the same view through the eyepiece. Unfortunately, my secondary mirror was loose in tightening it, I’ve managed to lose all semblance of an image. I need some daylight now to try to sort things out.
Ok, good luck sorting it out. Let us know what you find. It might help if you posted a photo of your equipment setup, as someone here on the forum might have an insight.
