Data Reduction Frequently Asked Questions

Are there any colour transformations available for the VIRCAM filters and another filter system?


The UK in-kind VIRCAM archive reprocessing and new ESO VIRCAM imaging pipeline use the 2MASS catalogue to astrometrically and photometrically calibrate the science fields. The colour transformations used for the conversion between the VIRCAM photometric system and the system used for photometric calibration (e.g. 2MASS) can be found in the fits tables included in the data distribution (HIERARCH ESO PRO CATG = PHOTCAL_TAB).

For the current VIRCAM detectors and filters, the transformations used in the PHOTCAL_TAB to the 2MASS filters are:

Z_VIRCAM           = 2.025*Jmag_2MASS - 1.025*Hmag_2MASS
Y_VIRCAM           = 1.610*Jmag_2MASS - 0.610*Hmag_2MASS
J_VIRCAM           = 0.923*Jmag_2MASS + 0.077*Hmag_2MASS
H_VIRCAM          = 0.032*Jmag_2MASS + 0.968*Hmag_2MASS
Ks_VIRCAM         = 0.010*Jmag_2MASS + 0.990*Kmag_2MASS
NB118_VIRCAM  = 1.100*Jmag_2MASS - 0.100*Hmag_2MASS
NB980_VIRCAM  = 1.680*Jmag_2MASS - 0.680*Hmag_2MASS 

Please, consult the website:
for updates on the relations.