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This will launch the xcombspec GUI. First, enter in your data path (which should be the "Object" directory in your reductions folder). Then specify the root filename (i.e. "Spec_") and the file numbers (range or comma delimited, e.g. "140-144,147"). Load the spectra and then follow the provided xcombine help instructions to finish the combine operation. This needs to be done for both your object and telluric. In many cases the SNR of the telluric is high enough to use a single exposure, but we still advise observers to combine dithered tellurics to avoid mitigate bad pixels.