calc_theta

acstools.polarization_tools.calc_theta(q, u, detector, pav3)

Calculate the position angle of the electric field vector given Stokes Q and U. For ACS, it is also necessary to supply the position angle of the V3 axis of the telescope (PA_V3 in the primary header) and the name of the ACS detector used.

Parameters:
  • q (float) – Stokes Q parameter.

  • u (float) – Stokes U parameter.

  • detector ({'wfc', 'hrc'}) – Name of the ACS detector used for the observation. Must be either WFC or HRC.

  • pav3 (float or Quantity) – Position angle of the V3 axis in units of degrees. Found in ACS primary headers with keyword PA_V3.

Returns:

theta – Position angle of the electric field vector in degrees.

Return type:

Quantity