cutout-fits 0.0.4

A package to produce cutouts of (remote) FITS files.

cutout-fits

A utility to produce cutouts of FITS images using astropy. Remotely-hosted FITS images a fully supported using ffspec and s3fs.

Installation

From PyPI (stable):

pip install cutout-fits

From git (latest):

pip install git+https://github.com/AlecThomson/cutout-fits.git

Usage

The command-line tool can be invoked using cutout-fits entry point. Currently, spatial cutouts are specified using a centre right ascension and declination along with a cutout radius. Spectral cutouts are specified with a start and end frequency range.

Any additional cube dimensions, such as time or Stokes, will simply be included in the cutout. Further, any non-image HDUs present in the FITS file will also be simply included in the output file.

$ cutout-fits -h
usage: cutout-fits [-h] [--freq-start FREQ_START] [--freq-end FREQ_END] [-o] [-v] infile outfile ra_deg dec_deg radius_arcmin

Make a cutout of a FITS file

positional arguments:
  infile                Path to input FITS file - can be a remote URL
  outfile               Path to output FITS file
  ra_deg                Centre RA in degrees
  dec_deg               Centre Dec in degrees
  radius_arcmin         Cutout radius in arcminutes

options:
  -h, --help            show this help message and exit
  --freq-start FREQ_START
                        Start frequency in Hz
  --freq-end FREQ_END   End frequency in Hz
  -o, --overwrite       Overwrite output file if it exists
  -v, --verbosity       Increase output verbosity

Further API documentation is provided on read the docs.

Remote files

If accessing a remote file on S3, you'll need to set your access keys. To do this, fsspec looks for the following environment variables:

FSSPEC_S3_ENDPOINT_URL='https://...'
FSSPEC_S3_KEY='...'
FSSPEC_S3_SECRET='...'

This project support using a .env file to store these variables, if needed. Simply set these variables in a .env files in your current working directory or set them in your environment if you wish. Be careful not to commit them to VCS.