Observations in the interferometric mode can be done using either cross-correlations or pointing scans. Using pointing scans, a correction from pointing errors is possible (see section ``Reduction method''). The procedure asks for the measurements of the gain USB/LSB value (same remark as above).
In addition to the brightest quasars mentionned above, several phase calibrators (secondary flux calibrators) are also selected by this procedure. The list is variable, but typically includes a few weaker sources frequently used on observing projects. For example in April 1992:
| 0851+202 |
| NRAO530 |
| 2200+420 |
| 3C120 |