Writing Spectra to a FITS file

Warning

FITS writer doesn’t work well after spectral slicing yet. In addition, reading fits files and writing the same files again might not give the exact same files, although the intended spectra will remain the same.

This page explains how to write spectra to FITS format. For more information on reading spectra and FITs in general, go to the FITS reader documentation page.

Currently the FITS writer only works with 1-D spectra objects. These objects include the linear spectra objects, or the multispec spectra objects (which are stored as a list of spectra). write_fits.write method deciphers the type of object passed automatically and writes spectra to the given file in FITS format. An example to write a simple linear FITS file:

>>> from specutils.io import read_fits, write_fits
>>> myspec = read_fits.read_fits_spectrum1d('myfile.fits')
>>> write_fits.write(myspec, 'mynewfile.fits')

Writing to a file in multispec FITS format is similar:

>>> from specutils.io import read_fits, write_fits
>>> spectra_list = read_fits.read_fits_spectrum1d('mymultispec.fits')
>>> write_fits.write(spectra_list, 'mynewmultispec.fits')

The multispec format supports various functions to map the pixel indices to dispersion. Currently the following multispec formats are supported:

  • Linear Dispersion Function
  • Log-linear Dispersion Function
  • Legendre Polynomial Dispersion Function
  • Chebyshev Polynomial Dispersion Function
  • Linear Spline Dispersion Function
  • Cubic Spline Polynomial Dispersion Function

Currently, modifications to the spectrum1D objects may not be correctly reflected in the output. In future, this will be fixed. Also it will be possible to write sliced spectrum based on index or dispersion, as well as spectrum which has been transformed from another kind of WCS.

Reference/API

specutils.io.write_fits Module

Functions

write(spectrum, filename[, clobber])