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THE REDUCTION OF FIBER-FED ECHELLE SPECTROGRAPH DATA: METHODS AND AN IDL-BASED SOLUTION PROCEDURE

Echelle spectrograph data present several challenges in data reduction. In this paper we address the general problem of accurately extracting spectra from a night's worth of raw CCD fiber-fed echelle data frames. We first briefly review echelle spectroscopy: properties of the basic echelle spectrograph, how the orders are arranged on the CCD, and what demands and constraints this data format places on reduction algorithms. We then discuss solutions to the various problems for fiber-fed data, with particular emphasison the removal of the scattered light background. Finally, we discuss our implementation of these solutions. We have written a package using the Interactive Data Language (IDL) that uses the methods described in this paper to give accurate extractions of spectra from fiber-fed echelle frames with any number of spectral orders of arbitrary tilt and curvature. We describe how interested persons may obtain the package through anonymous FTP.