4. Tips and Tricks

This is a collection of tips and tricks that can be useful for reducing different data, or to do it slightly differently from what is presented in the example.

4.1. Flatfields

4.1.1. Y, J, and H-bands

Flamingos-2 Y, J and H master flats are created from lamps-on and lamps-off flats. Both types are passed in together to the “reduce” command. The order does not matter. The software separates the lamps-on and lamps-off flats and use them appropriately.

4.1.2. K-band

For K-band master flats, lamp-off flats and darks are used. In that case both flats (lamp-off only for K-band) and darks need to be fed to “reduce”. The darks’ exposure time must match that of the flats. The first input file to “reduce” must be a flat for the correct recipe library to be selected. After that the software will sort out how to use the inputs appropriately to produce the flat. For example:

$ reduce @flats_K.list @darks_for_flats.list

The K-band thermal emission from the GCAL shutter depends upon the temperature at the time of the exposure, and includes some spatial structure. Therefore the distribution of emission is not necessarily consistent, except for sequential exposures. So it is best to combine lamp-off exposures from a single day.

4.2. Bypassing automatic calibration association

We can think of two reasons why a user might want to bypass the calibration manager and the automatic processed calibration association. The first is to override the automatic selection, to force the use of a different processed calibration than what the system finds. The second is if there is a problem with the calibration manager and it is not working for some reason.

Whatever the specific situation, the following syntax can be used to bypass the calibration manager and set the input processed calibration yourself:

$ reduce @sci_images.list --user_cal processed_dark:S20131120S0115_dark.fits processed_flat:S20131129S0320_flat.fits

The list of recognized processed calibration is:

  • processed_arc
  • processed_bias
  • processed_dark
  • processed_flat
  • processed_fringe
  • processed_standard