Calibration Check¶

Overview¶

We strongly recommend that one perform a calibration check with the .pypeit file before proceeding to run the reduction. This verifies that the number of desired calibration files exist and allows the user to examine how the code will group calibration files with science frames. It does not check the sanctity of the files nor process the calibrations in any manner.

calcheck¶

The procedure is simple. Add the following line to your .pypeit file:

run calcheck True

You must also verify that your .pypeit file does not include this line:

run setup True   # Cannot be set for calcheck or full reduction

Either set ‘run setup’ to False, comment it out, or remove it altogether.

You may then run PypeIt, e.g.:

run_pypeit kast_blue_setup_A.pypeit

The code will exit with error if there are insufficient calibration frames. Otherwise, it will exit after organizing the files and will produce a new .group file for your inspection.

You should confirm that the correct number of science and exposure standard files have been identified.

Settings¶

PypeIt identifies calibration files that are closest in time to every individual science frame. You can place an upper limit on the time window that PypeIt uses to search for calibrations but setting the keyword:

fits calwin 12.0

which will search for calibrations that were taken within +/-12 hours from a science frame. See docs on calwin for a further discussion.

The primary settings you need to specify at this stage are:

The number of calibration files required of each frametype
Over-ride any frametype designations, as necessary.
Modify the method(s) for bias subtraction, flat fielding etc.

For the second issue, see modifying_frametype.

For the first issue see below:

calwin¶

When associating calibration files to a given science frame, PypeIt will restrict to data within a window in time. This is specified by a calwin parameter which has a default value of 12 (hours) for most instruments. One can turn off this restriction by setting the value to 0 in the Spect block:

fits calwin 0

This is the default for Taking Calibrations for LRISb and may become the default for all instruments.

Calib number¶

The user can specify and/or over-ride defaults for the number of calibration frames required by adding a series of lines (or edit the existing ones) in the Spect block of the .pypeit file. One line per calibration frametype, as desired. Here is a block one might use for LRISb:

# Spect
spect read
 arc number 1
 trace number 5
 bias number 10
 standard number 1
 pixelflat number 3
spect end

When a positive, non-zero value is used, the code will require that there be that many calibration frames for each science frame reduced. And, PypeIt will restrict to precisely that many calibration files.

If you wish to use at least an input number of frames (and more if they exist), then specify the calibration number with a negative integer value, e.g.:

pixelflat number 5
arc number 1
trace number -5
bias number -5
standard number -1

Table of Contents