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astropy / specreduce

Tools for the reduction of spectroscopic observations from Optical and NIR instruments
https://specreduce.readthedocs.io
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Implement 2D sky subtraction using bivariate splines #193

Open tepickering opened 11 months ago

tepickering commented 11 months ago

This PR implements the Kelson (2003) technique for subtracting the sky background from 2D spectra without the need for rectification or interpolation.

codecov[bot] commented 11 months ago

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (aea9d50) 81.56% compared to head (4441b8d) 81.61%.

Additional details and impacted files ```diff @@ Coverage Diff @@ ## main #193 +/- ## ========================================== + Coverage 81.56% 81.61% +0.05% ========================================== Files 10 10 Lines 998 1001 +3 ========================================== + Hits 814 817 +3 Misses 184 184 ```

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chris-simpson commented 11 months ago

I really don't think this is an implementation of Kelson's method. You're fitting the BivariateSpline as a function of IMAGE pixel coordinates

spline_fit = LSQBivariateSpline(x.ravel(), y.ravel(), ...)

whereas Kelson says the spline should be fit as a function of x_r and y_r (page 694), coordinates which are orthogonal and aligned with the spatial and dispersion axes, using the known transformation from measuring the distortion from arc lamps or sky lines (page 691).