Gnuastro: Simulating The Exposure Map of a Pointing Pattern - Simulating the Exposure Map

9 May 2024


(1) Mohammad Akhlaghi, Centro de Estudios de F´ısica del Cosmos de Aragon (CEFCA), Plaza San Juan 1, 44001, Teruel, Spain {}.

Abstract and Intro

Simulating the Exposure Map

Acknowledgment and References



Within Gnuastro, the executable in charge of simulating the exposure map of a given list of pointings is called astscript-pointing- -simulate. As with all Gnuastro features, it has a complete documentation in Gnuastro’s manual[2] which is available in many formats (on the command-line, as web pages, PDF and etc). A complete and dedicated tutorial is also available within the tutorials chapter[3] of the manual.

Three of the images produced in the tutorial (as of version 0.21) are displayed in Figure 1. The left image shows the exposure map that is produced from a five-point, “+”-shaped set of pointings on the sky, with one pointing in the center and four on the outer extents. The middle image uses one of the hooks that are available within the script to produce a noisy image and not an exposure map. This hook can also be used to insert simulated/real objects. The right image shows how another hook can be used to account for trimming of the outer edges (which sometimes do not get exposed enough due to vignetting). This hook can also be used to insert any random area of bad pixels or to simulate persistence in near infra-red detectors (these can be large).

For its processing, this script needs two input files: 1) a table containing the RA and Dec of each pointing, 2) a FITS image from the camera that the dither pattern is meant for. The image has to contain the celestial world coordinate system (WCS, see Calabretta & Greisen 2002) headers. Having a WCS is very important, especially for cameras with a wide field of view, because distortions can become visible/significant.

The tutorial and dedicated manual for this script are available in the Gnuastro manual and will always be up to date with the running version; therefore for the practical details, we encourage readers to follow the Gnuastro manual. The future changes in the script that break with this research note will be clearly designated in a “changes after publication” subsection of the section describing this script.

This paper is available on arxiv under CC 4.0 DEED license.


[3] node/Tutorials.html