Total reduction of distorted echelle spectrograms: an automatic procedure.

We describe a semiautomatic procedure for the reduction of high-dispersion echelle spectra recorded with an image tube. The spectra are traced with a computer-controlled microdensitometer that scans along the curved spectral orders. The curvature of each order is calculated approximately by a FORTRAN program from known grating and distortion parameters. A typical spectrum includes 25 orders (covering 1500 A) and is traced with a slit 0.012 A wide. To produce an atlas of intensity vs wavelength and to determine the equivalent widths of 300 lines currently require a day. We discuss the reduction procedures and time requirements in detail.