We take the source extractor output on our calibration images and fit a 2nd order polynomial to the r = sqrt((x-x0)^2 + (y-y0)^2) values.
x0: 1428
y0: 976
M: 1.000000e+00 + 2.494829e-05 x + -3.899707e-07 x^2
B: 1.000000e+00 + 2.071482e-05 x + -3.729216e-07 x^2
G: 1.000000e+00 + 2.476901 e-05 x + -3.884373e-07 x^2
R: 1.000000e+00 + 2.650458e-05 x + -4.040382e-07 x^2
B:
R:
G:
M:
