parallactic_angle¶
-
simcado.utils.
parallactic_angle
(ha, de, lat=-24.589167)[source]¶ Compute the parallactic angle
- Parameters
- hafloat
[hours] hour angle of target point
- defloat
[deg] declination of target point
- latfloat
[deg] latitude of observatory, defaults to Armazones
- Returns
- parangfloat
The parallactic angle
Notes
The parallactic angle is defined as the angle PTZ, where P is the .. math:: taneta = frac{cosphisin H}{sinphi cosdelta - cosphi sindelta cos H} It is negative (positive) if the target point is east (west) of the meridian.
References
Ball: “A Treatise on Spherical Astronomy”, Cambridge 1908