SVDFIT: An IRAF Task for Eigenvector Sky Subtraction

A new method has been developed for estimating and removing the spectrum of the sky from deep spectroscopic observations. This method does not rely on simultaneous measurement of the sky spectrum with the object spectrum. The technique is based on the iterative subtraction of continuum estimates and eigenvector sky models derived from singular value decompositions of sky spectra and sky spectra residuals. IRAF tasks have been developed to implement this technique. Using simulated data derived from small-telescope observations, we demonstrate that the method is effective for faint objects on large telescopes.