The antenna gains can be further calibrated using the phase reference sources (0102+584 and 2202+422) interleaved in the observation track. After applying the antenna gains to the data, it is recommended to take out the continuum emission from the data using uvlin.
An image cube for the H30 line can be constructed from
the continuum-free data using invert, cleaned using
clean
and convolved with the clean beam using restor.
The final cleaned image cube of the H30
from NGC 7538 is shown
in Fig. 4.8.