Pinched optics?

[lukebl]

I can anyone confirm whether this a sign of pinched optics?

After cleaning my 10" Newt mirror yesterday, I reassembled it and took some images. This is a stack, but all of the individual frames show these triangular stars. I don't think it can be coma as I was using a coma corrector, and the funny-shaped stars are all over the image, including the middle, and at the same orientation.

I'm guessing I've tightened the mirror too tightly.

 

[R26 oldtimer]

Could it be sensor tilt?

[souls33k3r]

Are you in correct back focus? Did you install any additional/new extension tubes in between the focuser and your camera?  

[celestron8g8]

I think it's pinched optics for sure . Take a look at this video from YouTube . Looks exactly like what your image is showing . 

 

[lukebl]

Thanks folks. I think it probably is pinched optics. I've loosened the mirror clamps now, but after three clear nights in a row, it looks like the clouds will prevent me testing it for a week or two.

by the way, the galaxy is NGC 5746 which doesn't seem to be imaged very often. There is an annoying diffraction spike from 3rd magnitude 109 Virginis which is just off the edge of the frame.