Background correction

The specreduce.background module generates and subtracts a background image from the input 2D spectral image. The Background object is defined by one or more windows, where each window is a region parallel to a Trace, offset from that Trace by a specified separation in the cross-dispersion direction, and extending over a specified width (also measured along the cross-dispersion axis) in pixels. The object can be generated with:

• Background

• Background.one_sided

• Background.two_sided

The center of the window can either be passed as a float/integer or as a Trace.

bg = specreduce.background.Background.one_sided(image, trace, separation=5, width=2)

or, equivalently

bg = specreduce.background.Background.one_sided(image, 15, separation=5, width=2)

The background image can be accessed via bkg_image and the background-subtracted image via sub_image (or image - bg).

The background and trace steps can be done iteratively, to refine an automated trace using the background-subtracted image as input.