Combining Pre- and Post-August 1994 Data

In August 1994, the nominal flux density of the ATCA's primary flux calibrator, 1934-638, was revised to give better agreement between the ATCA's flux density scale and the flux scales used in the northern hemisphere (the VLA in particular). For more discussion, see John Reynolds' memo ``A revised flux scale for the AT Compact Array'' (AT Memo 39.3/040).

This introduces a problem when mixing data (either combining or just comparing) calibrated before and after this change. By default Miriad tasks use the new flux scale. However if you use the option `oldflux' in gpcal and mfcal when calibrating 1934-638, the old flux scale will be propagated to the calibrated data. In this way, new data can be calibrated to have the old flux scale, and so can be combined/compared directly with data calibrated before the revision.