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Galsim, make a box around each star to find the PSF
Rotate the ellipticity back around into the correct x,y frame
Coordinate transformation is the same as before to figure out the major/minor axes
2.20
- Ellipticity components
- Make new figure with running mean lines displayed for x/y source separation over 1000 images
Elana sent me a source that breaks down ellipticity and what it means.
I have a code block that calculates the ellipticity components e1 and e2 given the approximate coordinates of a star. I calculate ellipticity and its components e1 and e2 (stretching along x/y and y=x/y=-x). Once I calculate the components, the ellipse's major axis is at an angle a = 1/2 arctan(e2/e1) from the positive x-axis, so then I can calculate what the rotation of the focal plane was for this image, and from that back out this angle in that reference frame.