Data Reduction Frequently Asked Questions
Are there any colour transformations available for the VIMOS imaging filters and another filter system?
The UK in-kind VIMOS archive reprocessing and new ESO VIMOS imaging pipeline use the APASS catalogue to photometrically calibrate the standard star fields. The resulting zeropoint is then applied to the science images.
The colour transformations used for the conversion between the VIMOS-IMG photometric system and the system used for photometric calibration (e.g. APASS) can be found in the fits tables included in the data distribution (HIERARCH ESO PRO CATG = PHOTCAL_TAB), and are divided into two tables defining the transformations for the old VIMOS detector set and the current VIMOS detector set.
For the old VIMOS detectors (data prior to August 1, 2010) the transformations are:
Uvimos = 3.2 * gAPASS – 2.2 * rAPASS
Bvimos = 1.0 * BAPASS + 0.05 * gAPASS - 0.05 * rAPASS
Vvimos = 1.0 * VAPASS
Rvimos = 1.05 * rAPASS – 0.05 * gAPASS
Ivimos = 1.16 * iAPASS – 0.16 * rAPASS
zvimos = 1.65 * iAPASS – 0.65 * rAPASS
For the current VIMOS detectors (data post August 1, 2010) the transformations are:
Uvimos = 3.2 * gAPASS – 2.2 * rAPASS
Bvimos = 1.0 * BAPASS + 0.05 * gAPASS - 0.05 * rAPASS
Vvimos = 1.0 * VAPASS
Rvimos = 1.08 * rAPASS – 0.08 * gAPASS
Ivimos = 0.96 * iAPASS – 0.04 * rAPASS
zvimos = 1.65 * iAPASS – 0.65 * rAPASS