Photometric calibration observations are routinely carried out with all ESO imaging cameras in every clear night. The nightly zeropoints derived from these observations are accurate to about 10%. Recently, we have started the FORS Absolute Photometry Project (FAP) to investigate, if and how percent-level absolute photometric accuracy can be achieved with FORS1, and how such photometric calibration can be offered to observers. We found that there are significant differences between the sky-flats and the true photometric response of the instrument which partially depend on the rotator angle. A second order correction to the sky-flat significantly improves the relative photometry within the field. We demonstrate the feasibility of percent level photometry and describe the calibrations necessary to achieve that level of accuracy. © 2008 Springer-Verlag Berlin Heidelberg.
CITATION STYLE
Freudling, W., Möller, P., Patat, F., Moehler, S., Romaniello, M., Jehin, E., … Pompei, E. (2008). Photometry with FORS. In ESO Astrophysics Symposia (Vol. 2008, pp. 35–40). https://doi.org/10.1007/978-3-540-76963-7_4
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