Faster starfield subtraction, because when blurring the input data to match the blur inherent in the reprojections, instead of reprojecting the input data into its own frame twice, the data is simply blurred with a Gaussian of the appropriate size.
The WCS for the starfield map can be passed into build_starfield_estimate, instead of using the auto-generated one.
Full Changelog: v0.0.3...v0.0.4