compute_va_effects_vector

stcal.velocity_aberration.compute_va_effects_vector(velocity_x, velocity_y, velocity_z, u)[source]

Compute velocity aberration effects scale factor.

Computes constant scale factor due to velocity aberration as well as corrected RA and DEC values, in vector form.

Parameters:

  • velocity_x (float) – The components of the velocity of JWST, in km / s with respect to the Sun. These are celestial coordinates, with x toward the vernal equinox, y toward right ascension 90 degrees and declination 0, z toward the north celestial pole.

  • velocity_y (float) – The components of the velocity of JWST, in km / s with respect to the Sun. These are celestial coordinates, with x toward the vernal equinox, y toward right ascension 90 degrees and declination 0, z toward the north celestial pole.

  • velocity_z (float) – The components of the velocity of JWST, in km / s with respect to the Sun. These are celestial coordinates, with x toward the vernal equinox, y toward right ascension 90 degrees and declination 0, z toward the north celestial pole.

  • u (numpy.ndarray) – The vector form ([u0, u1, u2]) of right ascension and declination of the target (or some other point, such as the center of a detector) in the barycentric coordinate system. The equator and equinox should be the same as the coordinate system for the velocity.

Returns:

  • scale_factor (float) – Multiply the nominal image scale (e.g., in degrees per pixel) by this value to obtain the image scale corrected for the “aberration of starlight” due to the velocity of JWST with respect to the Sun.

  • u_corr (numpy.ndarray) – Apparent position vector ([ua0, ua1, ua2]) in the moving telescope frame.