Additional information on reference pointing
There are two POINTING types which can be used for reference pointing:
- UPDATE determines the pointing offsets with respect to the currently installed pointing solution.
- REFPNT causes the global pointing parameters to be reloaded prior to determining the pointing offsets.
When reference pointing at 3mm, it is possible that the global solution will be so bad that the reference pointing will not work. For this reason, it is preferable to use POINTING=UPDATE at 3mm, so that once you have the pointing approximately correct, you can continue to reference point.
WARNING! The problem with using UPDATE is that if the pointing gets badly corrupted, all further pointing solutions will fail, and the corrupted solutions will be retained. For this reason it is advised to use UPDATE only at 3mm. Also, KEEP A CLOSE WATCH ON YOUR CALIBRATOR AMPLITUDES!!
WARNING! There is currently a bug in CATAG, in that if you perform a REFPNT and then immediately after do another REFPNT, it will not reload the global solution.
In the even of solutions getting corrupted, reload the global pointing parameters.
A few other notes:
- SCHED doesn't know how to calculate the drive time for pointing observations, and sets it to zero.
- CATAG doesn't handle bin-mode observations.
- Unless you are pointing at a maser with a line-width significantly narrower than 8MHz, use CONFIG=FULL_128_2.
- When pointing on a continuum source, use CONFIG=FULL_128_2.
- When pointing on a continuum source, make sure the dual frequencies are adjacent or the same. The reference pointing offsets are governed by the first frequency.
If you start CATAG, but when you do so it exits with the message
Checking for other CATAG processes...
ERROR: CATAG heartbeat detected.
Another CATAG process must still be about.
then someone else is running CATAG. Instructions on how to remove a CATAG session are available here.
CATAG also produces a diagnostic line for each integration.
CAOBS> set point_antennas 12345
would use only antennas 1-5.
WARNING! There is currently a bug in the CAOBS/CATAG antenna selection; if you don't want to use an antenna for pointing, you should stow it! If you are paranoid, set point_antennas as well.
Original: Dave Rayner (2001)
Modified: Bob Sault (6-Sep-2003), Phil Edwards (21-Oct-2008)