gszasz / true-ecs

Calculates valid ECS coordinates (RA, DEC) from the image coordinates (X, Y) using corrected WCS parameters.

True-ECS

Calculates valid ECS coordinates (RA, DEC) from the image coordinates (X, Y) using corrected WCS parameters. This code is handy for the automated ex-post astrometric corrections of large amounts of photometric measurements.

To determine correct WCS parameters, True-ECS queries Astrometry.net service via API. Astrometry.net ignores WCS parameters provided by the FITS header. Instead, it directly cross-matches a dozen sources in the image using pattern recognition and then uses these positions to determine the correct WCS parameters inversely. Since the method is agnostic to the original WCS transform parameters, it covers many real-life scenarios that would otherwise be hard to solve.

Installation

1. Clone repository and change into the project directory.

git clone https://github.com/gszasz/true-ecs.git
cd true-ecs

2. Copy the example config.yaml into the project directory.

cp examples/config.yaml .

3. Open the file with your favorite text editor and put there your personal API key from the Astrometry.net. Change directory and filenames so they would reflect your data-file structure. You can use glob patterns and {target} placeholer that will be replaced by name of the current target. List all your targets in the list of targets.

Usage

Program has no command line options. All options are defined by by the config.yaml configuration file.

./true-ecs.py

License

True-ECS is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

True-ECS is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with True-ECS. If not, see https://www.gnu.org/licenses/.  The use of a range of years within a copyright notice in this distribution should be interpreted as being equivalent to a list of years including the first and last year specified and all consecutive years between them.

For example, a copyright notice that reads "Copyright (C) 2005, 2007-2009, 2011-2012" should be interpreted as being identical to a notice that reads "Copyright (C) 2005, 2007, 2008, 2009, 2011, 2012" and a copyright notice that reads "Copyright (C) 2005-2012" should be interpreted as being identical to a notice that reads "Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012".