Affiliation
American Association of Variable Star Observers (AAVSO)
Wed, 02/09/2022 - 00:59
I have a few images of U Mon where the WCS solution is wrong, off by somewhere between 0.5 and 2 degrees. It's odd because it only seems to affect the B filter images. So far, all V, SR and I images taken at the same time are fine. If it helps, the file names for some of the afflicted files are 637796523461939013.fts, 637785274078584478.fts and 637780112350883824.fts, or I can share them with someone who could research the problem. VPhot claims that the images are all WCS-solved, and the WCS headers are definitely there, just wrong.
Shawn (DKS)
Shawn:
That certainly is a strange one! Sometimes the first image in a series may be poorly centered but it should have corrected on the following images since it was very far from the desired center location. Hopefully, it is a one time glitch?
Please share images with MZK and SGEO.
Ken
Shawn:
Does this target yield an image with only a few stars in the B filter? It may not even plate-solve when taken, so the scope cannot be initially pointed correctly until the V filter image with more stars?
However, perhaps VPhot/PinPoint was able to plate-solve it later after it was uploaded? Guessing?
Ken
Thanks, Ken. I've shared two of the failing B images along with the V images taken immediately after them. These are very short exposures, but this is a rich star field so there are dozens of stars visible. The images are clean and sharply focused - basically, they look just like the images taken the day before or after that solve correctly.
Shawn