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ratt-ru / pfb-imaging

Preconditioned forward/backward clean algorithm
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Incorporate average beam pattern during imaging (Mosaicing) #1

Open landmanbester opened 4 years ago

landmanbester commented 4 years ago

Because of the way the algo is structured it should be trivial to incorporate an average primary beam pattern in the measurement model. This should be better than an image space PB correction because it is formulated as a forward model. My main reason for wanting this is to make mosaics. The algorithmic structure should make this quite natural. You basically need to keep track of a PSF and primary beam pattern for unique PHASE_DIR. I think it should be as simple as rephasing the measurement sets and then making primary beam patterns with the centre of the beam at the individual phase centres. @o-smirnov does that sound correct or am I missing something? I think the w-term should be taken care of by the gridder as long as the measurement sets are correctly rephased, something that is easy to do using the prep_data.py script

landmanbester commented 4 years ago

We also need this for the SPI fitter https://github.com/ratt-ru/pfb-clean/issues/8

landmanbester commented 4 years ago

For reference, the phase and w-screen shifting required for the wgrider should be easy to test with the python implementation of the wgridder given here

https://gitlab.mpcdf.mpg.de/mtr/ducc/-/blob/ducc0/python/demos/wgridder_python_implementations.py

landmanbester commented 1 year ago

About time I get back to this. I want to start by using a single beam for all antennas so I'm trying to incorporate the average MeerKAT primary beam patterns here

https://archive-gw-1.kat.ac.za/public/repository/10.48479/wdb0-h061/index.html

From the pdf document I assume we need to flip the beam pattern vertically before adding parallactic angle rotation etc. Anyone know what the correct convention is? Pinging @o-smirnov @bennahugo @IanHeywood

bennahugo commented 1 year ago

Believe it is upside down - ie. south through east. Two notes:- you still need to apply an antidiagonal to the visibilities to make them right way up.

Also note that the phasing in L-band is correct. The phasing in S is reversed so the polarization response goes north through west before hv phase correction

On Mon, Nov 6, 2023, 07:02 Landman Bester @.***> wrote:

About time I get back to this. I want to start by using a single beam for all antennas so I'm trying to incorporate the average MeerKAT primary beam patterns here

https://archive-gw-1.kat.ac.za/public/repository/10.48479/wdb0-h061/index.html

From the pdf document I assume we need to flip the beam pattern vertically before adding parallactic angle rotation etc. Anyone know what the correct convention is? Pinging @o-smirnov https://github.com/o-smirnov @bennahugo https://github.com/bennahugo @IanHeywood https://github.com/IanHeywood

— Reply to this email directly, view it on GitHub https://github.com/ratt-ru/pfb-clean/issues/1#issuecomment-1794891739, or unsubscribe https://github.com/notifications/unsubscribe-auth/AB4RE6TOOFEZIA7QTZMATHLYDDUXBAVCNFSM4MKWX6NKU5DIOJSWCZC7NNSXTN2JONZXKZKDN5WW2ZLOOQ5TCNZZGQ4DSMJXGM4Q . You are receiving this because you were mentioned.Message ID: @.***>

landmanbester commented 1 year ago

Thanks @bennahugo. It sounds like a bit of a nightmare getting this right for the full polarisation response, especially if we want to combine data from multiple bands. Do you know of a memo or paper documenting the conventions for MeerKAT anywhere? It would be great if we can make all bands consistent upfront

bennahugo commented 1 year ago

Evla memo 219 for discription of handedness phasing and conventions.

I'm not sure whether the beams are correctly calibrated for phasing. By the sounds of it there is still an uncalibrated differential phase and the measured holography. Check in with Mattieu on this.

On Tue, Nov 7, 2023, 12:59 Landman Bester @.***> wrote:

Thanks @bennahugo https://github.com/bennahugo. It sounds like a bit of a nightmare getting this right for the full polarisation response, especially if we want to combine data from multiple bands. Do you know of a memo or paper documenting the conventions for MeerKAT anywhere? It would be great if we can make all bands consistent upfront

— Reply to this email directly, view it on GitHub https://github.com/ratt-ru/pfb-clean/issues/1#issuecomment-1799804883, or unsubscribe https://github.com/notifications/unsubscribe-auth/AB4RE6U3TUZT24LKG42K6N3YDKHJ5AVCNFSM4MKWX6NKU5DIOJSWCZC7NNSXTN2JONZXKZKDN5WW2ZLOOQ5TCNZZHE4DANBYHAZQ . You are receiving this because you were mentioned.Message ID: @.***>