Chgcentre

[d3v-null]

Argument for vis convert

[cjordan]

Acktschually, an argument for InputVisArgs.

If it were me, I'd add a new struct member phase_centre: RADec to InputVisParams, and the value is set by the user argument to InputVisArgs, or if it's not specified, obs_context.phase_centre. Then all aspects of the code that currently use obs_context.phase_centre use input_vis_params.phase_centre instead.

Finally, the phase centre change actually needs to happen. I'd probably make a function that takes the old and new phase centres and an arbitrary chunk of visibilities, multiplying them by the correct factor. The work should probably be done immediately after each call to read_timestep in src/params/input_vis.rs. Check if any phase rotation needs to happen at all as it's not cheap.

The phase centre should be clarified as always being in the J2000 frame.