The Spectrum Extraction window is activated by clicking on the button in the Main window and contains options for fitting the sky and extracting spectra. The various options and parameters of this window are described in Sections G.3.6 and G.3.7 of this Appendix and in Chapter 6, Vol. B of the MIDAS User Guide.
The window provides two buttons and for an interactive definition of the limits of the sky and the object. Clicking one of the these buttons activates a cursor in the display window. Two positions, corresponding sequentially to the lower and upper limits, are expected for the object. Four values are expected for the sky, defining two zones usually located below and above the spectrum. Positions must be clicked from the bottom to the top of the frame. When the expected number of positions has been selected, a SET/LONG command initializing the object or sky limit keywords (OBJECT, LOWSKY, UPPSKY) is sent to MIDAS.
The sky can be fitted on a spectrum by clicking on . A file selection list pops up for selection of the input file. The name of the resulting sky file is defined in the text field Sky (image or constant): which includes the default value sky.
Spectrum extraction can be performed by simple row average or using an optimal extraction algorithm with the two buttons and . Clicking on one of those buttons pops up a list of .bdf files in the directory. Click the name of the selected file. A small prompt window appears requesting the name of the output file. The default is the input file name with the suffix _obj.