Monday, February 9, 2009

Watch out for those FreqIDs!

If you're a continuum observer (especially if you use the single-channel, 50 MHz correlator setting at the VLA), it's important to remember when reducing line data that each different set of frequencies in line data is given its own FreqID number. Some tasks work fine with datasets with multiple FreqIDs (e.g., LISTR), but other tasks (e.g., TVFLG or SPFLG) need to be told what FREQID to use or they won't find the data. You can control how the FREQIDs are assigned in FILLM.


Adrienne said...

If you're reducing line data taken with the EVLA, there's the added "feature" that AVSPC (for making a new, correct CH 0) claims to work with FREQID -1 but actually does not work! So if you have interference from galactic HI in your data, and observe your calibrators at different frequencies than your source, this makes your life quite difficult. Just ask me how I know.

Adrienne said...

By "EVLA" I mean during the VLA-EVLA transition of course.