mag += etmag
mag += nom_at_ext
# Can now calculate the zp array
zp = refmag - mag
zperr = np.sqrt(refmagerr*refmagerr + magerr*magerr)
# Trim values out of zp where the zeropoint error is > 0.1
zp_trim = np.where((zperr<0.1), zp, None)
zperr_trim = zperr[np.flatnonzero(zp_trim)]
refmag_trim = refmag[np.flatnonzero(zp_trim)]
refmagerr_trim = refmagerr[np.flatnonzero(zp_trim)]
zp_trim = zp[np.flatnonzero(zp_trim)]
nzp = float(ad.nominal_photometric_zeropoint())
plt.figure(1)
# Plot the mag-mag plot
plt.subplot(2,2,1)
plt.scatter(refmag, mag)
plt.errorbar(refmag, mag, xerr=refmagerr, yerr=magerr, fmt=None)
plt.xlabel('Reference Magnitude')
plt.ylabel('Instrumental Magnitdute')
# Plot the mag - zp plot
plt.subplot(2,2,2)
plt.scatter(refmag, zp)
plt.errorbar(refmag, zp, xerr=refmagerr, yerr=zperr, fmt=None)
plt.scatter(refmag_trim, zp_trim, color='g')
