A Python module for aligning the spectra in different flat-fielded images of an IMSET. These files can then be combined with along-the-slit dithering to reject hot pixels and cosmic rays. The POSTARG2 keyword is used to determine the number of rows to be shifted.

stistools.sshift.shiftimage(infile, outfile, shift=0)

Shift each image extension of an input file by N rows and write the new image extension to the output file.

stistools.sshift.sshift(input, output=None, shifts=None, platescale=None, tolerance=None)

Align spectra from different images of an imset.

input : list

A list of input filenames. These must be STIS flat- fielded (_flt) image FITS files. This argument will accept a single filename or a list of filenames.

shifts : list, optional

A list of integers indicating the number of rows to shift each image of each file in the cross-dispersion (Y-) direction.

platescale : float, optional

The size of a pixel in arcseconds. Used to convert the value of the POSTARG2 keyword to pixels.

tolerance : float, optional

The allowed difference between calculated shifts and integer pixel shifts (fraction of pixel).

output : list, optional

A list of output filenames. The number of output filenames must match the number of input filenames. If no output is given, then the _flt substring of the input file is replace by the _sfl substring to create an output file. This option will accept a single filename or a list of filenames.


  • Paul Barrett (STScI)