Data Reduction Frequently Asked Questions

In reducing some FORS2 MXU spectra, we are using a star which was observed in MOS mode to flux-calibrate the spectra. For chip1, everything is OK, but chip 2 fails. Why?

In the MOS observations on the standard star, the standard is located on chip 1. Therefore the chip 1 data has to be used to determine the spectral response function for both chips, so you will have to use the chip 1 data for input, even when reducing the chip 2 data.