|
[QUOTE=Atmos;1344553]It's largely masked by shooting on both sides of meridian. The attached plot is taken from 29 drizzled frames from one side of meridian. Although it looks like a tilt issue, this largely remains unchanged even when fiddling with the built in tip/tilt plate.
On arrival one of the bolts that holds the tip/tilt plate in place was very tight and I eventually found out that it shouldn't have been. This is the first image I took after I backed that bolt of 0.6mm to get the backplate within ~100 microns of flat using a digital depth gauge. Before backing off the bottom right corner was just terribly out of focus (maybe 200 microns) compared to the top left corner. Also getting maybe 2% vignetting on the left hand side of the frame and up to 11% on the right.
Something is shifting when you go on the other side of the meridian do you mean?
F3 would be touchy collimation. Tiny changes would be the go.
If you are using an OAG then the pick off mirror can easily create a big shadow. I had one on my RHA for a while until I raised the pick off prism and it went away! F3 means the light rays are at a steep angle and that will cause the prism to cast a larger shadow. Perhaps check this is not the case.
Greg.
|