If using hour angles instead of RA, (H_1 - H_2) works similarly.
This is essential for planning double-star observations, conjunction events, or calculating the field of view of an instrument. Given: Date and local civil time. Find: Local sidereal time (LST) to set equatorial mount.
Apply the spherical law of cosines to the PZS triangle:
Altitude (h = 0°) (center of body).
