Focus/Collimation issue

[lazjen]

Well, I think it's a collimation issue.

Setup is GSO RC10 at native FL, so around 2000 mm. No reducers or flatteners. Camera is ASI1600.

See the images below. I think my collimation is whacked, but I'm not sure what needs adjusting as it looked lined up in the tak scope. I've got a rotator on the system (nitecrawler), so if I rotate the image using it, the "defect" rotates as expected.

256751

256750

Any pointers appreciated.

[multiweb]

That trefoil looks like a pinch somewhere. Maybe secondary bonding.

[Camelopardalis]

I see a similar effect with my newt when it's not in harmony with ambient...

[lazjen]

I'm fairly certain it's not going to be ambient temperature related - this was probably 1 - 2 hr after starting that I took those images.

I had thoughts it might be something pinched from some searches, but I was hoping it wasn't. :) I guess I will need to pull the scope apart. Hopefully just the secondary will sort it out.

[Atmos]

The out of focus image still looks like the collimation might be off a bit. In focus certainly looks like trefoil but out of focus doesn't look quite collimated yet either.

[lazjen]

At this point, it's probably: "why not both?"

Have to wait until it cools down a bit to pull the scope apart - too hot in the dome. :)

[multiweb]

You can get a pinch at low temperature if the mirror or lens cell contracts around the glass.