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- Arc line identification: firehose_ld will by default cross-correlate your arc frame against our NeNeAr template and attempt an automatic wavelength solution. This works fairly well but not 100% of the time. If you trust the software, you can choose "fully automated." Or, you can choose "user reidentify." The latter option generates a first guess ID of "good" lines, and then launches a GUI for the user to check centroiding, and generate the final wavelength fit. Use of this GUI is documented in the Arcs page of the Wiki.
- Flat field interaction: There is not much user-intervention allowed here, but if you choose "inspect results" an atv window will pop up to let you see the quality of the composite flat. Usually this is mostly useful to see whether your red/blue transition row was chosen judiciously.
- Red/blue transition row: As described above, firehose_ld generates a superflat from a composite of dome flats of different lamp voltages. Depending on your exposure times, the temperature of the dome, etc, the row (i.e. the y pixel number) where the transition optimally blends from one flat to the other may vary. We have chosen y=1150 as a default, but the user may set this to another value as needed.