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MWATelescope / Birli

A Rust library for preprocessing tasks in the Murchison Widefield Array (MWA) data pipeline.
Mozilla Public License 2.0
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phasing to pointing centre is only valid at the midpoint of the observation #164

Open d3v-null opened 2 weeks ago

d3v-null commented 2 weeks ago

--pointing-centre will grab the RA Dec of the pointing centre according to the metafits using Marlu RADec::from_mwalib_tile_pointing, this is only valid at the start of the observation. The pointing centre is fixed in Azimuth / Elevation, not RADec.

andreww5au commented 2 weeks ago

There are two RA/Dec coordinate pairs in the metafits file - the primary beam coordinate is calculated for the observation midpoint time, but the phase centre coordinate (the RA and Dec entered on the command line) is used as the phase centre for fringe stopping for the entire observation. They are typically 5-10 degrees apart on the sky.

RA and DEC - coordinates of primary beam pointing centre (typically a 'sweet spot' near the target of interest), in degrees, calculated for the MIDPOINT TIME of the observation.

RAPHASE and DECPHASE - the coordinates of the desired target, in degrees. These cards will not be present if the observation was scheduled for a fixed Alt/Az, or using raw beamformer dipole delays.