Pinched optics?

[Greggles]

Hi All,

Recently cleaned by 10" Dobsonian mirror and took the scope out for the first time tonight.

Quick question, collimation is not perfect but is this pinched optics or just the clips visible when completely out of focus? For the life of me I cant remember if i could always see the clips or not.
Photos attached. in focus still looking pretty good when imaging a star.

On a side note, cleaning went pretty well.. i think.. some streaking on the mirror despite being rinsed with demineralized water, but i''ve heard that's not an issue.

pretty terrible seeing here in Sydney tonight but iI pointed the scope to a low Saturn and it was the worst that i've ever seen. Hope its the seeing and not the optics.

Cheers

Greg

[mswhin63]

Need a corrector for vignetting to suit your camera and scope combination.

[Greggles]

Yep agreed been contemplating it for a while. Quite happy with my level of imaging with a dobsonian, not sure if I should get one. Also think it will effect my focus and I've already had to move the mirror up to get focus with my DSLR.

Any thoughts about the pinched optics regarding clips visible when out of focus?

[Saturnine]

The seeing is terrible tonight, whenever we have strong westerly winds it's almost a given.
The 3 notches you see are the shadows of the mirror clips and nothing to be concerned about. The optics do not seem to be pinched, usually shows as a triangular out of focus star test image. Google pinched optics and check the images of the different aberrations presented as examples.
Your collimation is slightly out as the secondary shadow is slightly off centre, a bit of fine tuning will sort that out.

[Greggles]

Thanks Jeff for the confirmation.

Yep my laser collimator is not perfect was planning on fixing collimation tonight but clouds set in before I had a chance to do anything.

Ehhhh the Sydney weather has been so bad lately I was desperate to get out tonight.