hour angle
Star's westward displacement
Hour angle is an astronomical coordinate measuring the angular distance of a celestial body from the observer's meridian, expressed in hours, minutes, and seconds rather than degrees.
It indicates how long ago (or until) an object crossed the highest point in its arc across the sky.
The hour angle changes continuously as Earth rotates, unlike fixed celestial coordinates.
- celestialOf the sky above
- celestial equatorSphere's midplane above us
- meridianPole-to-pole great circle
- siderealOf the stars
- transitMovement between places
zenith · equator · celestial sphere · longitude · latitude · time zone · telescope · observatory · sundial · noon · midnight · epoch · ephemeris · equinox · polar · rotation · Earth · stars
- celestial navigationcelestial navigation, sextant, astrolabe, nautical almanac, celestial sphere
- astronomical tablesephemeris, astronomical tables, moon phases, lunar phases, sunset times
- navigationcompass, compass rose, signs, charts, navbar
- spherical geometrygreat circle, great circles, geodesic, geodesics, lune
- sundial partsgnomon, shadow, motto, Roman numerals