StarID.compute_pointing

giant.stellar_opnav.star_identification:

StarID.compute_pointing()

This method computes the right ascension and declination of an axis of the camera frame in units of degrees.

The pointing is computed by extracting the camera frame z axis expressed in the inertial frame from the a_priori_rotation_cat2camera and then converting that axis to a right ascension and declination. The conversion to right ascension and declination is given as

\[\begin{split}ra=\text{atan2}(\mathbf{c}_{yI}, \mathbf{c}_{xI})\\ dec=\text{asin}(\mathbf{c}_{zI})\end{split}\]

where atan2 is the quadrant aware arc tangent function, asin is the arc sin and \(\mathbf{c}_{jI}\) is the \(j^{th}\) component of the camera frame axis expressed in the Inertial frame.

In general this method is not used by the user as it is automatically called in the query_catalogue() method.

Returns:

The right ascension and declination of the specified axis in the inertial frame as a tuple (ra, dec) in units of degrees.

Return type:

Tuple[float, float]