- sherpa.astro.ui.get_backscal(id=None, bkg_id=None)
Return the BACKSCAL scaling of a PHA data set.
Return the BACKSCAL setting 1 for the source or background component of a PHA data set.
backscal – The BACKSCAL value, which can be a scalar or a 1D array.
- Return type
number or ndarray
The BACKSCAL value can be defined as the ratio of the area of the source (or background) extraction region in image pixels to the total number of image pixels. The fact that there is no ironclad definition for this quantity does not matter so long as the value for a source dataset and its associated background dataset are defined in the similar manner, because only the ratio of source and background BACKSCAL values is used. It can be a scalar or be an array.
“The OGIP Spectral File Format”, Arnaud, K. & George, I. http://heasarc.gsfc.nasa.gov/docs/heasarc/ofwg/docs/spectra/ogip_92_007/ogip_92_007.html
>>> get_backscal() 7.8504301607718007e-06 >>> get_backscal(bkg_id=1) 0.00022745132446289