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cbassa/crota.py

Created November 4, 2019 22:01
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FITS WCS rotation angles
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crota.py
#!/usr/bin/env python3
import sys
import numpy as np
from astropy.wcs import wcs
w = wcs.WCS(sys.argv[1])
sx = np.sqrt(w.wcs.cd[0, 0]**2+w.wcs.cd[0, 1]**2)*3600.0
sy = np.sqrt(w.wcs.cd[1, 0]**2+w.wcs.cd[1, 1]**2)*3600.0
ang1 = np.arctan2(w.wcs.cd[0, 1], w.wcs.cd[0, 0])*180.0/np.pi
ang2 = np.arctan2(-w.wcs.cd[1, 0], w.wcs.cd[1, 1])*180.0/np.pi
print("scale: %gx%g arcsec, rotation: %g, %g deg" %(sx, sy, ang1, ang2))
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