Sidereal hour angle, used in celestial navigation, is similar to right ascension, but increases westward rather than eastward.
From the en.wikipedia.org
However, the use of only one circumference unwittingly implies only one rotation in inertial space, so the corresponding time unit must be a sidereal hour.
From the en.wikipedia.org
The cycle's begin position, the stellar position and sidereal hour timing the eclipse, are used by later astronomers for calibrating their observations in relation to subsequent eclipses.
From the en.wikipedia.org
The hour angle of the vernal point is, by definition, the observer's sidereal time.