Automated Object Finding / Tracing
For the large majority of programs, FIREHOSE's automated object finder and spectral tracing code should work very well. To turn on this mode, select either "Fully Automated" or "Inspect Results" under object finding preferences in the preferences pane.
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If "Inspect results" is active, an xatv window will launch at completion. This shows the sky-subtracted frame, with the object highlighted in a solid black line, and the +/- 2 sigma limits of the profile shown in dotted black lines.
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Manually Defined Traces
If automated object finding did not work properly, or your object is very faint, or other bright objects appear on the slit, you may need to intervene manually in the object finding process.
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Failing that, it is possible to force the software to use exactly the aperture and trace you command, via the "User Specify" mode.
User Initial Guess Mode
To specify an object in user initial guess mode, the software performs first-pass sky subtraction, and then launches an after-market version of atv modified for this purpose. The view below shows an example make using a brown dwarf spectrum:
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To select the left hand object, zoom in, place the cursor on the object of interest, and press the space bar. A cross will appear indicating the location of your selection, as shown here:
You can specify multiple locations, although there is no particular advantage to doing so. The software will take the median x-value of the selections and use that as an initial guess for the trace finding code. Once you have selected your object, press 'q' or click 'Done' and the code will trace your selection. When it has finished, it will plot up the results: 
Here the solid line shows the object profile, and the dotted lines indicate the +/- 2 sigma boundaries of the fitted extraction aperture.
If you are happy with the result, move on to object extraction. If not, then you can try your hand at fully manual apertures, described next.