gijzelaerr
commented
10 years ago Original comment thread migrated from bugzilla
at 2013-02-27 19:51:12 Tony Willis replied:
CASA (and the lwimager) offer one the option to combine multiple spectral windows together for a single operation. e.g. CASA clean offers the option
spw -- Select spectral window/channels
NOTE: channels de-selected here will contain all zeros if
selected by the parameter mode subparameters.
Channel selection behaves differently in clean (e.g. The multiple
ranges are not supported yet).
default: ''=all spectral windows and channels
spw='0~2,4'; spectral windows 0,1,2,4 (all channels)
spw='0:5~61'; spw 0, channels 5 to 61
spw='<2'; spectral windows less than 2 (i.e. 0,1)
spw='0,10,3:3~45'; spw 0,10 all channels, spw 3,
channels 3 to 45.
spw='0~2:2~6'; spw 0,1,2 with channels 2 through 6 in each.
In scripts like calico-view-ms, at present one can only select a single spectral window for display. It would be nice to combine windows into a single display if they have closely adjacent frequencies. In fact, on the display side, I think that this facility may already be present - I recall JEN and Maaijke wanting to look at multiple LOFAR bands in one display.
My reason for requesting this is that the DRAO telescope writes out UV FITS files which get translated into four spectral window ids at 21 cm because we have four bands which are close together in frequency. However the frequency steps are not uniform so we cannot write out a single spwid with four frequency channels.
at 2013-02-27 19:51:12 Tony Willis reported:
need a way to specify multiple spectral window IDs together