"""
desitarget.photo
================
Implements the photometric transforms between SDSS and DECam using g,r,z
documented in DESI-1788v1
https://desi.lbl.gov/DocDB/cgi-bin/private/ShowDocument?docid=1788
"""
[docs]def sdss2decam(g_sdss, r_sdss, i_sdss, z_sdss):
"""
Converts SDSS magnitudes to DECam magnitudes
Args:
[griz]_sdss: SDSS magnitudes (float or arrays of floats)
Returns:
g_decam, r_decam, z_decam
Note: SDSS griz are inputs, but only grz (no i) are output
"""
gr = g_sdss - r_sdss
ri = r_sdss - i_sdss
iz = i_sdss - z_sdss
# - DESI-1788v1 equations 4-6
g_decals = g_sdss + 0.01684 - 0.11169*gr
r_decals = r_sdss - 0.03587 - 0.14114*ri
z_decals = z_sdss - 0.00756 - 0.07692*iz
return g_decals, r_decals, z_decals
[docs]def cfht2decam(g_cfht, r_cfht, i_cfht, z_cfht):
"""
Converts CFHT magnitudes to DECam magnitudes
Args:
[griz]_cfht: CFHT magnitudes (float or arrays of floats)
Returns:
g_decam, r_decam, z_decam
Note: CFHT griz are inputs, but only grz (no i) are output
"""
gr = g_cfht - r_cfht
ri = r_cfht - i_cfht
iz = i_cfht - z_cfht
# - DESI-1788v1 equations 1-3
g_decals = g_cfht - 0.03926 + 0.05736*gr
r_decals = r_cfht - 0.07371 - 0.13004*ri
z_decals = z_cfht - 0.08165 - 0.20494*iz
[docs]def decam2sdss(g_decam, r_decam, z_decam):
"""Not yet implemented"""
raise NotImplementedError
[docs]def decam2cfht(g_decam, r_decam, z_decam):
"""Not yet implemented"""
raise NotImplementedError