caput.interferometry

Useful functions for radio interferometry.

Coordinates

Interferometry

caput.interferometry.fringestop_phase(ha, lat, dec, u, v, w=0.0)[source]

Return the phase required to fringestop. All angle inputs are radians.

Note that for a visibility V_{ij} = < E_i E_j^*>, this expects the u, v, w coordinates are the components of (d_i - d_j) / lambda.

Parameters

  • ha (array_like) – The Hour Angle of the source to fringestop too.

  • lat (array_like) – The latitude of the observatory.

  • dec (array_like) – The declination of the source.

  • u (array_like) – The EW separation in wavelengths (increases to the E)

  • v (array_like) – The NS separation in wavelengths (increases to the N)

  • w (array_like, optional) – The vertical separation on wavelengths (increases to the sky!)

Returns

phase – The phase required to correct the fringeing. Shape is given by the broadcast of the arguments together.

Return type

np.ndarray

caput.interferometry.ground_to_sph(x, y, lat)[source]

Get the CIRS coordinates.

Latitude is given in radians. Assumes z is positive

Parameters

  • x (array_like) – The East projection of the angular position

  • y (array_like) – The North projection of the angular position

  • lat (array_like) – The latitude of the observatory.

Returns

ha, dec – Hour Angle and declination in radians

Return type

array_like

caput.interferometry.projected_distance(ha, lat, dec, x, y, z=0.0)[source]

Return the distance project in the direction of a source.

Parameters

  • ha (array_like) – The Hour Angle of the source to fringestop too.

  • lat (array_like) – The latitude of the observatory.

  • dec (array_like) – The declination of the source.

  • x (array_like) – The EW coordinate in wavelengths (increases to the E)

  • y (array_like) – The NS coordinate in wavelengths (increases to the N)

  • z (array_like, optional) – The vertical coordinate on wavelengths (increases to the sky!)

Returns

dist – The projected distance. Has whatever units x, y, z did.

Return type

np.ndarray

caput.interferometry.sph_to_ground(ha, lat, dec)[source]

Get the ground based XYZ coordinates.

All input angles are radians. HA, DEC should be in CIRS coordinates.

Parameters

  • ha (array_like) – The Hour Angle of the source to fringestop too.

  • lat (array_like) – The latitude of the observatory.

  • dec (array_like) – The declination of the source.

Returns

x, y, z – The projected angular position in ground fixed XYZ coordinates.

Return type

array_like