The reduction of grating spectra is quite straightforward (certainly when compared to attacking échelle spectra) but doing it well requires careful work. Fortunately, the programs needed to do this have already been written, so it is simply a matter of setting them up and watching them go. However, the setup can be complex and, as it varies for different datasets, requires a bit of time.
In this document I give the detailed instructions needed to reduce CCD grating spectroscopy using Tom Marsh's packages pamela and molly, which requires some pre-processing using Starlink software. This is probably not the easiest to use (but also not the most difficult), but it is fairly straightforward and gives (as far as we know) the best results of any package around.
These instructions are for UNIX/Linux systems, and I will assume that you have already got pamela and molly and Starlink correctly installed, and that you are using the /bin/tcsh shell in your terminal.
You need to initialise the pamela commands by typing pamela at the command line. You will probably also need to type starlink, depending on how it is set up on your computer system. Individual Starlink packages are not automatically initialised so at various points you will probably also have to type kappa or figaro or convert to access some of the commands in this document.
This document is intended as a step-by-step guide and explanation, and so should complement the on-line documentation for pamela, molly, Starlink, and the Starlink packages kappa, figaro and convert.
Things enclosed in square brackets [ and ] indicate that you need to insert the relevant information without the square brackets.
I will be grateful to hear of any useful hints which could be added, and mistakes or misspellings which should be corrected in this document.
Preparation of the initial fits files:
Reducing the files and extracting the spectra:
Wavelength and flux calibration:
Summary checklist and examples: