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The currently used standard equinox and epoch is J2000.0, which is January 1, 2000 at 12:00 TT. The prefix "J" indicates that it is a Julian epoch. The previous standard equinox and epoch was B1950.0, with the prefix "B" indicating it was a Besselian epoch. Before 1984 Besselian equinoxes and epochs were used.
The difference between reference to an epoch alone, and a reference to a certain equinox with equator or ecliptic, is therefore that the reference to the epoch contributes to specifying the date of the values of astronomical variables themselves; while the reference to an equinox along with equator/ecliptic, of a certain date, addresses the ...
The equinox which occurs near the first day of spring (with respect to the North hemisphere) is called the vernal equinox. The vernal equinox can be used as a principal direction for ECI frames. [4] The Sun lies in the direction of the vernal equinox around 21 March.
In the astrological age that preceded the time of Hipparchus, the vernal equinox had taken place when the Sun was in the constellation of Taurus, and during that previous epoch the constellations of Canis Minor (The Dog), Hydra (The Snake), Corvus (The Raven), and Scorpius (The Scorpion) – that is, the constellations that correspond to the ...
In order to reference a coordinate system which can be considered as fixed in space, these motions require specification of the equinox of a particular date, known as an epoch, when giving a position in ecliptic coordinates. The three most commonly used are: Mean equinox of a standard epoch
In order to fix the exact primary direction, these motions necessitate the specification of the equinox of a particular date, known as an epoch, when giving a position. The three most commonly used are: Mean equinox of a standard epoch (usually J2000.0, but may include B1950.0, B1900.0, etc.)
When seen from above – a view seen during an equinox for the first time from the Cassini space probe in 2009 – they receive very little sunshine; indeed, they receive more planetshine than light from the Sun. [43] This phenomenon occurs once every 14.7 years on average, and can last a few weeks before and after the exact equinox. Saturn's ...
The longitude of the ascending node (bright green) as a part of a diagram of orbital parameters.. The longitude of the ascending node, also known as the right ascension of the ascending node, is one of the orbital elements used to specify the orbit of an object in space.