Data Reduction Frequently Asked Questions
I prefer to subtract the sky with external routines (i.e. in the case of extended objects that cover most of the slit(s), or dedicated sky observations). What are the relevant files I should use for this purpose?
The fors_science product MAPPED_ALL_SCI_LSS contains the image with rectified and wavelength calibrated slit spectrum. This spectrum is not flux calibrated.
External routines for sky subtraction can be applied to MAPPED_ALL_SCI_LSS.
After the sky subtraction the SPECPHOT_TABLE product can be used to perform the flux calibration. The relevant columns in the table are "wave" and "response", which can be used to apply the response curve and obtain the desired sky-subtracted and flux-calibrated spectrum.