Startup
To start the longslit pipeline, from an IDL prompt type:
IDL> firehose_ld
where the _ld stands for low-dispersion. This should bring up the following window:
SETUP DIRECTORIES: The first step is to enter in exposure file names for each of the fields listed. The Raw directory should point to the folder where the 2D fits files reside. The Reductions directory is where the final data and intermediary files for calibration are generated and stored. The Raw and Reduction directories may be set to any location on disk where you want these files to reside. FIREHOSE never over-writes raw data, but we advise against performing reductions in the raw data directory as a precaution.
OBJECT file: This denotes a science frame. The software performs sky subtraction on a fram-by-frame basis, NOT with A-B-B-A sets. Only one file at a time is handled although we will loop on these in the next release.
ARC file: This is a wavelength calibration image. Our default is to use a NeNeAr combination, which has produced stable wavelength solutions. An arc line identification plot for this lamp combination may be found here; associated references for the line lists are here.
BLUE and RED flats: As in many spectrographs which cover a large wavelength range, it is difficult to obtain a single flat field exposure the covers the full spectral range at adequate signal-to-noise ratio without saturating. To work around this problem the pipeline takes in pairs of flats which we denote as "blue" and "red." These are obtained using different voltage settings on the variable quartz lamp in the Baade dome.
The "red" flat provides suitable counts for the red half of the spectrum but has too few counts in the blue; this is typically taken at low lamp voltage (we use 1.2 V).
The "blue" flat provides suitable counts in the blue half but saturates the red end of the spectrum. This is taken at higher lamp voltage (i.e. hotter,we use 2.2 V)
Enter in file names for each of these; if you only have one flat then put the same name in both fields and it will be fine. The software simply combines the two 2D frames, using a smooth weighting function to transition from one frame to the other without discontinuities.
Preferences
Once your file names are entered in, you will probably want to set preferences for the reduction stages. To do this, select the "Options->Preferences" pane from the menu bar. This will realize the following window:
