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 
and 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.
Figure: Spectrum Extraction window