As higher frequencies (particularly 
20 GHz) it is important to make
corrections for atmospheric opacity and gain-elevation effects.
Note that currently the elevation is not written correctly into Tidbinbilla rpfits files. This means that gain-elevation and opacity corrections will not work until a work around is implemented.
Gain-elevation curves for some telescopes and frequencies are known to ASAP (currently only for Tidbinbilla at 20 GHz). In these cases making gain-corrections is simple. If the gain curve for your data is not known, the user can supply either a gain polynomial or text file tabulating gain factors at a range of elevations (see help scantable.gain_el).
Examples:
ASAP> scans.gain_el() # If gain table known ASAP> scans.gain_el(poly=[3.58788e-1,2.87243e-2,-3.219093e-4])
Opacity corrections can be made with the global function opacity. This should work on all telescopes as long as a measurement of the opacity factor was made during the observation.
ASAP> scans.opacity(0.083)
Note that at 3 mm Mopra uses a paddle wheel for Tsys calibration, which takes opacity effects into account (to first order). ASAP opacity corrections should not be used for Mopra 3-mm data.