Verschueren, W. ; Hensberge, H.

published in Astronomy and Astrophysics, 240, pp. 216-222 (1990)

Abstract: The standard MIDAS reduction package have been investigated for echelle spectra using CASPEC CCD data obtained in the blue wavelength region. A number of numerical limitations, present in some reduction steps, are found to reduce the final accuracy attainable with the instrument. In a first paper, a new algorithm for a more precise wavelength calibration was described. Here, three new algorithms are presented, operating within the MIDAS environment, for order detection, background subtraction and order extraction, and compared with the standard procedures. It is shown that the proposed algorithms eliminate the ripple induced by integration over inclined orders and allow a more accurate representation of the background light distribution over the frame. The basic ideas behind the improvements are generally applicable to the reduction of other echelle data.

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