knows enough about the ATCA and a select group of other
telescopes to provide some nominal values
for parameters that FITS does not store - for example a system
temperature of 50 K and a system gain of 13 Jy/K are stored with ATCA
also attempts to estimate the integration time.
Unfortunately given the information present in a FITS file, this
integration time estimate is little better than an educated guess. Task
gives a message informing you of the values it is using. If
you know better values for system temperature, integration time, etc, than
those guessed by fits, you may wish to correct the stored values.
This is largely so that any noise estimates produced by later tasks are in more
meaningful units. You can correct these with the task puthd.
writes an item into the visibility dataset, which
overrides the value of a visibility variable with the same name. The
following three parameter boxes show the inputs to puthd
correct the system temperature to 80 K, the system gain to 11 Jy/K and
the integration time to 15 seconds.
|Parameter is dataset name followed by `systemp'
|Set to 80 K. Express it as a real number.
|Parameter is dataset name followed by `jyperk'
|Set to 11 Jy/K. Express it as a real number.
|Parameter is dataset name followed by `inttime'
|Set to 15 sec. Express it as a real number.
AIPS FITS files from the ATCA sometimes contain other flaws which Miriad issues warnings about - these can usually be safely ignored. These flaws
include visibilities with zero weight, incorrect apparent RA and DEC and
circular polarizations from the ATCA.