the angle, measured westward through 360°, between the celestial meridian of an observer and the hour circle of a celestial body.
the angular distance along the celestial equator from the meridian of the observer to the hour circle of a particular celestial body
The angular distance, measured westward along the celestial equator, between the celestial meridian of the observer and the hour circle passing through a celestial body. A body’s hour angle is measured in hours, minutes, and seconds, and corresponds to its right ascension as measured with respect to the observer’s meridian (which changes with time) rather than the vernal equinox (which is fixed on the celestial equator). A celestial object that crossed the observer’s meridian 3 hours and 20 minutes ago has an hour angle of +3 hours 20 minutes. An object that will not cross the meridian for another 3 hours and 20 minutes has an hour angle of -3 hours 20 minutes.
noun, Astronomy. 1. a great circle on the celestial sphere passing through the celestial poles and containing a point on the celestial sphere, as a star or the vernal equinox. noun 1. a great circle on the celestial sphere passing through the celestial poles and a specified point, such as a star hour circle A […]
[ouuh r-glas, -glahs, ou-er-] /ˈaʊərˌglæs, -ˌglɑs, ˈaʊ ər-/ noun 1. an instrument for measuring time, consisting of two bulbs of joined by a narrow passage through which a quantity of sand or mercury runs in just an . adjective 2. having a notably slim or narrow waist, midsection, or joining segment: She has an hourglass […]
- Hourglass contraction
hourglass contraction hour·glass contraction (our’glās’) n. Constriction of the middle portion of a hollow organ, such as the stomach or the uterus.
- Hourglass murmur
hourglass murmur n. A murmur in which there are two areas of maximum loudness, one preceding and the other following a softer midpoint. Its graph resembles an hourglass.