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Right ascension is measured eastward up to 24 h along the celestial equator from the primary direction. Right ascension (abbreviated RA; symbol α) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the (hour circle of the) point in question above the Earth. [1]
In this case, the longitude is also called the right ascension of the ascending node (RAAN). The angle is measured eastwards (or, as seen from the north, counterclockwise) from the FPA to the node. [2] [3] An alternative is the local time of the ascending node (LTAN), based on the local mean time at which the spacecraft crosses the equator.
Vega's proper motion is 202.03 ± 0.63 milliarcseconds (mas) per year in right ascension—the celestial equivalent of longitude—and 287.47 ± 0.54 mas/y in declination, which is equivalent to a change in latitude. The net proper motion of Vega is 327.78 mas/y, [83] which results in angular movement of a degree every 11,000 years.
The value of a solar beta angle for a satellite in Earth orbit can be found using the equation = [ + ()] where is the ecliptic true solar longitude, is the right ascension of ascending node (RAAN), is the orbit's inclination, and is the obliquity of the ecliptic (approximately 23.45 degrees for Earth at present).
Using a suitable prediction formula, the state ... Inclination (degrees) 51.6416 4: 18–25: Right ascension of the ascending node (degrees) 247.4627 5: 27–33:
Epsilon Eridani has a high proper motion, moving −0.976 arcseconds per year in right ascension (the celestial equivalent of longitude) and 0.018 arcseconds per year in declination (celestial latitude), for a combined total of 0.962 arcseconds per year. [1] [note 5] The star has a radial velocity of +15.5 km/s (35,000 mph) (away from the Sun ...
Right ascension is usually measured in sidereal hours, minutes and seconds instead of degrees, a result of the method of measuring right ascensions by timing the passage of objects across the meridian as the Earth rotates. There are 360° / 24 h = 15° in one hour of right ascension, and 24 h of right ascension around the entire ...
Were the Sun to be observed from this star system, it would appear to be a magnitude 2.55 star in the constellation Aquila with the exact opposite coordinates at right ascension 19 h 39 m 18.11950 s, declination −05° 13′ 29.9552″.