scopesim.optics.image_plane_utils.sub_pixel_fractions

scopesim.optics.image_plane_utils.sub_pixel_fractions#

scopesim.optics.image_plane_utils.sub_pixel_fractions(x, y)#

Make a list of pixel coordinates and weights to reflect sub-pixel shifts.

A point source which isn’t centred on a pixel can be modelled by a centred PSF convolved with a shifted delta function. A fraction of the delta function in moved into each of the adjoining pixels. For example, a star at (x,y)=(0.2, 0.2) would be represented by a following pixel weights:

---------------
| 0.16 | 0.04 |
---------------
| 0.64 | 0.16 |
---------------

where (0,0) is the centre of the bottom-left pixel

Given (x,y) pixel coordinates, this function returns the fractions of flux that should go into the surrounding pixels, as well as the coordinates of those neighbouring pixels.

Parameters:
Returns:

x_pix, y_pix, fracs – The x and y pixel coordinates and their corresponding flux fraction

Return type:

list of (int, int, float)

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