[bug #59324] Erroneous values of rotation and scaling for some quads

[Mohammad Akhlaghi]

Follow-up Comment #3, bug #59324 (project gnuastro):

Great! Thanks for the wonderful description in the comment Sachin ;-). The
results also look very promising (except for the signs).

The fact that some scale factors have become negative is very strange. There
must be a small mistake somewhere.

Infact, this observation pointed me to something interesting: the signs of the
scaling factor and theta are the same: anywhere that the scaling is negative,
theta is also negative. 

I'd love to look closely into the code and try it, but since your mind is
already fresh on it, I am sure you'll find it sooner ;-). 

Other than the negative values, I don't see any major outliers and probably a
sigma-clipped median can be used to find the over-all rotation and scaling. 

Once these are found, the only other element that we need to construct the WCS
is to choose a reference point and save its pixel coordinates (CRPIX1 and
CRPIX2) and ra/dec coordinates (CRVAL1 and CRVAL2) coordinates. The only thing
is that we want this point to have no distortion (for now: close to the center
of the image).

The first round of the job will then be complete. But we still have some
important problems to fix: 1) a robust way to build *the same* quads from
multiple catalogs and 2) account for distortion. Can you define two tasks for
these (if they aren't already)? 

For the distortion, once we have the reference point, we move all the (x/y)s
and (ra/dec)s to be centered around that. Then see how much their RA/Dec
differs from a raw rotation/scaling.

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