Instrument Settings

This document will detail aspects of the instrument settings files used in PypeIt.

These are mainly notes for the lead developers.

Generating a new settings file

Here is a quick cookbook of the steps involved:

  • Update Mosaic properties (e.g. lon, lat)
  • Update Detector properties * RN, GAIN are hard-coded to match detector
  • Update checks (note: white spaces are removed in this check) * CCD name * You must check NAXIS is 2 in “checks to perform”.
  • Update Keyword identifiers

Examine the base set of keywords in the data/settings/settings.basespect file and update for the instrument as necessary. Here are some of the standard ones:

keyword target 01.OBJECT               # Header keyword for the name given by the observer to a given frame
keyword idname 01.OBSTYPE              # The keyword that identifies the frame type (i.e. bias, flat, etc.)
keyword time 01.MJD-OBS                # The time stamp of the observation (i.e. decimal MJD)
keyword date 01.DATE-OBS               # The date of the observation (in the format YYYY-MM-DD  or  YYYY-MM-DDTHH:MM:SS.SS)
keyword equinox None                   # The equinox to use
keyword ra 01.RA                       # Right Ascension of the target
keyword dec 01.DEC                     # Declination of the target
keyword airmass 01.AIRMASS             # Airmass at start of observation
keyword naxis0 01.NAXIS2               # Number of pixels along the zeroth axis
keyword naxis1 01.NAXIS1               # Number of pixels along the first axis
keyword exptime 01.EXPTIME             # Exposure time keyword
  • Update FITS properties
    • timeunit refers to the format of the time KEYWORD (e.g. mjd)
    • We should give a few examples here
  • Fiddle with rules for Image type ID. Below are some helpful guidelines
    • Again, check the settings.basespect file first
    • Common check or match rules to update include
      • arc match decker any – One frequently uses a narrow slit for arcs
      • xxx match dispangle |<=## – Add if your disperser has a variable angle
    • If a keyword is specified in science/pixflat/blzflat/trace/bias/arc frames it must also appear in the Keyword identifiers list.
    • If a keyword value contains only some interesting value, you can split the keyword value using the ‘%,’ notation. For example, suppose you have the string 10:50:23.45, and you’re interested in the 50 for a match condition, you would use ‘%’ to indicate you want to split the keyword value, ‘:’ indicates the delimiter text, ‘1’ indicates you’re interested in the 1st argument (0-indexed), ‘<60’ is an example criteria. Each of these should be specified in this order, separated by commas, so the final string would be: %,:,1,<60 If you want to split on multiple delimiters, separate them with a logical or operator. For example, if you want to split a string at the characters ‘:’ and ‘.’, you would use the expression %,:|.,1,<60
    • If the text ‘|’ appears in the match condition, the absolute value will be taken. For example ‘|<=0.05’ means that a given keyword’s value for a calibration frame must be within 0.05 of a science frame’s value, in order to be matched.
    • If a keyword’s value contains spaces, replace all spaces with one underscore.
    • If the header contains two keyword’s of the same name, only the value of the first one will be recognised.
  • Run
  • Add arc solution * set debug[‘arc’] = True in run_pypeit
  • Add extinction file if a new observatory * Add file in data/extinction * Edit README
  • Add test suite