Celestial navigation glossary
Sidereal hour angle (SHA)
A star’s angle west of Aries; nearly constant, listed on the daily pages.
Where the course teaches it
The stars, and the first point of Aries, in the module Latitude from Polaris. Find your latitude at twilight from the Pole Star, with the Polaris tables.
Taught alongside it
- Ecliptic
- The Sun’s yearly path among the stars, tilted 23.44° to the celestial equator; it crosses the equator going north at Aries.
- First point of Aries (♈)
- The reference point among the stars; a star’s GHA is GHA Aries plus its SHA.
- Polaris
- The pole star, within a degree of the celestial pole: its altitude is close to your latitude.