celestial+equator
81Great circle — For fictional interstellar organization called Great Circle, see Andromeda (novel). A great circle divides the sphere in two equal hemispheres A great circle, also known as a Riemannian circle, of a sphere is the intersection of the sphere and a… …
82Orion (constellation) — For other uses, see Orion (disambiguation). Orion Constellation List of stars in Orion Abbreviation Ori Genitive Orionis …
83Minute of arc — This article is about geometry. For firearms terminology, see Minute of Angle. A minute of arc, arcminute, or minute of angle (MOA), is a unit of angular measurement equal to one sixtieth (1⁄60) of one degree. In turn, a second of arc or… …
84Proper motion — The proper motion of a star is its angular change in position over time as seen from the center of mass of the solar system.[1] It is measured in seconds of arc per year, arcsec/yr, where 3600 arcseconds equal one degree.[2] This contrasts with… …
85Extraterrestrial skies — The sky of a world refers to the view of the heavens from its surface. This view varies from world to world for many reasons. The most important factor in the appearance of a world s sky is its atmosphere, or the lack thereof. Depending on the… …
86ecliptic — ecliptically, adv. /i klip tik/, n. 1. Astron. a. the great circle formed by the intersection of the plane of the earth s orbit with the celestial sphere; the apparent annual path of the sun in the heavens. b. an analogous great circle on a… …
87Orion — /euh ruy euhn/, n., gen. Orionis /awr ee oh nis, or , euh ruy euh nis/ for 2. 1. Class. Myth. a giant hunter who pursued the Pleiades, was eventually slain by Artemis, and was then placed in the sky as a constellation. 2. Astron. the Hunter, a… …
88equatorial system — A set of celestial coordinates based on the celestial equator as the primary great circle. It is usually expressed as declination and an hour angle or a sidereal hour angle. Also called an equinoctial system of coordinates or a celestial equator… …
89Northern Hemisphere — Coordinates: 45°0′0″N 0°0′0″E / 45°N 0°E / 45; 0 …
90North Star — The North Star is the prominent pole star that lies closest in the sky to the north celestial pole and which appears (approximately) directly overhead to an observer at the Earth s North Pole; currently, this is Polaris. The North Star lies about …
