#73 use WEIGHT column if WEIGHT_SPECTRUM is not available

[Oleg Smirnov]

Getting the dreaded WARNING: This measurement set has no or an invalid WEIGHT_SPECTRUM column; all visibilities are assumed to have equal weight..

These are MSs coming out of the JVLA pipeline here that for whatever reason only have a WEIGHT column, which does not have a spectral axis. Reading the MS definition, I interpret this as legal.

Would it be easy to implement this logic in WSCLEAN? If WEIGHT_SPECTRUM is available, use it, else if WEIGHT is available, use it (implicitly expanding the frequency axis), else fall back to equal weights?

[André Offringa]

I checked the MS definition ( http://casa.nrao.edu/Memos/229.html ) and WEIGHT_SPECTRUM is indeed an optional column. The 'scalar' WEIGHT column should be used if it doesn't exist. I've now implemented this and pushed it to Git, queued for 1.12.