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ECH_COUNT

Function

To count the orders present in a data frame.

Summary

This routine counts the number of orders in an echellogram. The method used is to first collapse or median filter the central 20 columns of the input frame into a 1-D array, and then apply a triangle filter to this array. The autocorrelation function is then calculated and the peak (corresponding to average order separation) is located. The central columns are then resampled using a box scaled according to the expected order size. A triangle function of appropriate dimension is then convolved with the array and the resluting array is smoothed. A search is then made for the local peak values representing the approximate order centres.

Available Topics

Hints

Martin Clayton
mjc@star.ucl.ac.uk
Mon Dec 9 17:09:34 1996