For a WCS returns pixel scales along each axis of the image pixel at the CRPIX location once it is projected onto the “plane of intermediate world coordinates” as defined in Greisen & Calabretta 2002, A&A, 395, 1061.
Note
This function is concerned only about the transformation “image plane”->”projection plane” and not about the transformation “celestial sphere”->”projection plane”->”image plane”. Therefore, this function ignores distortions arising due to non-linear nature of most projections.
Note
In order to compute the scales corresponding to celestial axes only, make sure that the input WCS object contains celestial axes only, e.g., by passing in the celestial WCS object.
Parameters: | wcs : WCS
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Returns: | scale : ndarray |