Calibration Overview

This document gives an overview of the calibration steps of PypeIt. There is additional documentation for several of the more complex steps.

Sequence of Events

Here is the sequence of events:

Step	Products	Description
datasec	datasec image	2D image describing the detector pixels for analysis

datasec

In this step, PypeIt parses the instrument settings file (or user input) to establish the region on each detector for analysis. The overscan section is also established and is included in the datasec if one exists.

A 2D image defining the datasec pixels is generated and stored internally (in _datasec).

Standard

The standard approach to defining the datasec is to set these in the instrument settings file. It is necessary to generate one set per amplifier as each of these may have distinct properties (e.g. readnoise, gain).

Here are the values for Kast blue:

det01 numamplifiers 2                 # Number of amplifiers
det01 datasec01 [:,0:1024]
det01 oscansec01 [:,2049:2080]
det01 datasec02 [:,1024:2048]
det01 oscansec02 [:,2080:2111]
det01 gain 1.2,1.2                    # Inverse gain (e-/ADU)
det01 ronoise 3.7,3.7                 # Read-out noise (e-)

LRIS

The FITS file writing for LRIS is sufficiently complex that the datasec definition (and file loading) is guided by a custom method: arlris.read_lris()