Closed Joshuaalbert closed 3 months ago
I don't think that the last line in your example will hold except in a handful of very, very artificial configurations. vis2dirty
and dirty2vis
are adjoint to each other, but that doesn't translate into them being inverses of each other up to some factor.
I'm not really sure how the adjoint normalising factor is defined. If you can point me to some relevant literature, I'll try to provide a more useful answer.
I'm looking to understand the units and flux-scale of the produced dirty image.
Maybe this helps: the effect of vis2dirty
and dirty2vis
is equivalent (up to the small losses of accuracy due to the wgridding algorithm) to the explicit DFTs in the ducc
test files: https://github.com/mreineck/ducc/blob/4619f34f2c96dd6c28be961df4d436f484d51147/python/test/test_wgridder.py#L34-L90.
It's just the plain DFT, no additional factors are involved.
Thanks for pointing to this test. It's clear that it's just computing the DFT. I'll reopen if I have anything else.
Am I correct that the adjoint normalising factor for
vis2dirty
is4 / (num_freqs * (4 * num_rows - sqrt(8 * num_rows + 1) - 1))
such that,