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The Statistics Menu

The Statistics menu allows the user to define windows and perform statistical operations on data within these windows. These include cross sections in X and Y, made by collapsing a window onto the X or Y axis. These functions perform differently depending upon whether they are operating on IPCS data or CCD data, for IPCS data they sum the data in the perpendicular direction, whereas for CCD data they average them. This difference must be borne in mind when, for instance, estimating count rates per pixel for IPCS data, and estimating atmospheric transparency from a CCD spectrum of a spectrophotometric standard. At present only two windows are available for all data screens and all buffers, these remain in place until adjusted with the SET WINDOW options, even when the user switches between IPCS and CCD data. A future enhancement will provide separately defined windows for each data buffer.

With the X-CUT and Y-CUT functions it is possible to perform a preliminary sky subtraction. To do this Window 1 is placed on the object spectrum, and Window 2 on a suitable sky area. It is not necessary to make Window 2 exactly the same width as Window 1, as appropriate scaling is applied. It is not necessary to place Window 2 precisely in the spectral direction, as the limits in this direction of the sky region are changed to those of Window 1.

Options available from the Statistics menu are:-


next up previous contents
Next: The Screens Menu Up: The Menu Structure Previous: The Display Menu

manuals store
Wed Sep 17 12:36:20 BST 1997