OPTIMAL EXTRACTION OF CROSS-DISPERSED SPECTRA

Two algorithms are presented for direct optimal extraction from unstraightened images taken with cross-dispersed spectrographs. In the first, a virtual resampling takes place to calculate the weights appropriate for individual pixels. This algorithm has been implemented and extensively tested for the analysis of data taken with two recently commissioned instruments and produces a significant improvement compared with the conventional extraction. A second algorithm in which no resampling takes place is briefly discussed.