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Because it is a right-handed system, ecliptic longitude is measured positive eastwards in the fundamental plane (the ecliptic) from 0° to 360°. Because of axial precession , the ecliptic longitude of most "fixed stars" (referred to the equinox of date) increases by about 50.3 arcseconds per year, or 83.8 arcminutes per century, the speed of ...
Ecliptic coordinates are convenient for specifying positions of Solar System objects, as most of the planets' orbits have small inclinations to the ecliptic, and therefore always appear relatively close to it on the sky. Because Earth's orbit, and hence the ecliptic, moves very little, it is a relatively fixed reference with respect to the stars.
The equatorial describes the sky as seen from the Solar System, and modern star maps almost exclusively use equatorial coordinates. The equatorial system is the normal coordinate system for most professional and many amateur astronomers having an equatorial mount that follows the movement of the sky during the night.
The position of the Sun in the sky is a function of both the time and the geographic location of observation on Earth's surface. As Earth orbits the Sun over the course of a year, the Sun appears to move with respect to the fixed stars on the celestial sphere, along a circular path called the ecliptic.
Visual conjunction between the Moon and the planet Venus, the two brightest objects in the night sky. In astronomy, a conjunction occurs when two astronomical objects or spacecraft appear to be close to each other in the sky. This means they have either the same right ascension or the same ecliptic longitude, usually as observed from Earth. [1] [2]
The Right ascension of the star is about 18 h. 18 h means it is a March early-hours star and in blue sky in the morning. If 12 h RA, the star would be a March all-night star as opposite the March equinox. If 6 h RA the star would be a March late-hours star, at its high (meridian) at dusk.
It is on the celestial equator at both the left and right extremes of the sky chart, with the ecliptic (the orange dotted sine curve) passing through it. The first point of Aries , also known as the cusp of Aries , is the location of the March equinox (the vernal equinox in the northern hemisphere, and the autumnal equinox in the southern ...
The ecliptic coordinate system specifies positions relative to the ecliptic (Earth's orbit), using ecliptic longitude and latitude. Besides the equatorial and ecliptic systems, some other celestial coordinate systems, like the galactic coordinate system , are more appropriate for particular purposes.