14.8 Self calibration by a point source

In some cases the continuum is a point source, and is strong enough to be used to reference the phases and amplitudes of the line data. The phase and amplitude referencing can be done in CLIC command STORE PHASE /SELF or in the $uv$ tables using task UV_ASCAL.

For this one creates separately a line table and a continuum table. Naturally both must have been observed simultaneously. It is strongly advised to self-calibrate the phase first, then the amplitude using a longer smoothing time. UV_ASCAL allows in addition to subtract (part of) the input reference source, typically to provide continuum-free spectral line maps.

Note that this operation will work also if the source is somewhat extended, but with central symmetry; in that case only the phases can be self-calibrated.