...
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:
Note that there are two objects on the slit for this exposure. We are interested in the brighter of the two but could specify either for extraction.
Also, you may notice the relatively poor quality of the sky subtraction. Don't worry: this is the first attempt, and the final version used for spectral extraction will be much better. This iteration is only being used for object finding.
...