Fix Version/s: None
Investigate how to fit a final tweak to the WCS from tangent-plane/IWCS produced by
DM-20188 to the Sky allowing for tweaks to on sky positions and affine transform.
- is triggering
DM-20371 Create new shift/rot only WCS fitter
Looks good to me!
Are you planning to just use a standard (e.g. scipy optimizer) for the fit steps, or did you have some other way of predicting the rotation matrix and new crval from the last iteration?
Yeah, I think that was the plan. The matcher current just uses optimize.least_squares for it's minimizing and I can't imagine this needing anything better really.
So quick question, should we close this ticket and open a new one for the work on me coding this up? If so who watching this ticket wants to say they reviewed it?
Giving this to you as you said the overall design looked good.
John Parejko and had a few chats about how to fit the final WCS that includes only a shift/rotation and possibly a small stretch. Thankfully most of the functions we need to create everything are exposed in python through ast-shim.
The plan we came up with is to postpend a fitted 2D matrix transform to the already existing transform between the ast Frame just before the "IWC" frame to take care of any rotation and possible "squish". In addition to this we will fit the crvals on the "Sky" frame. The fitting would be done a total of 6 variables and would minimize the distance between reference positions on the sky to the predicted source locations on sky. This leaves every part of the WCS produced by Parejko's createInitialWcs function intact save for the initial crvals.
The steps to fit would be:
Parejko was also helpful enough to write a small example of getting the frames and creating a new WCS