A coordinate used on the celestial sphere just as longitude is used on Earth. An object's right ascension is measured in hours and minutes eastward from the vernal equinox.
The axis of rotation of an Equatorial telescope mount aligned with the earth's axis of rotation. It's calibrated in in 24 hour segments, since the Earth takes 24 hours to complete one rotation.
the arc on the celestial equator extending eastward from the vernal equinox to the meridian of the object in question in the equatorial coordinate system. This coordinate corresponds to longitude on the Earth. The other coordinate in this system is called "declination."
Measurement along the equator in astrology.
the angular distance east/west on the sky.
Angle, measured eastward, from the vernal equinox to the footof a star's hour circle.
Celestial equivalent of longitude. Measured in 24 hour segments divided across the sky. Also see declination.
The east-west coordinate in the equatorial coordinate system. The right ascension is measured in units of hours, minutes, and seconds to the east from a fixed direction in the sky, which itself is defined as the line of intersection of the ecliptic and the celestial equator.
In the Equatorial coordinate system, a number representing the angle measured eastward, along the Celestial Equator, from the Vernal Equinox to the hour circle through a star. Somewhat analogous to longitude, in the Terrestrial coordinate system, but measured only to the east, and in time units, instead of degrees.
the angle of a star's location along the celestial equator away from the vernal equinox, an imaginary star positioned at the intersection between the celestial equator and the ecliptic. Measured in the same way as hour angle. See an astronomy text for more information.
angular distance on the celestial sphere measured eastward along the celestial equator from the equinox to the hour circle passing through the celestial object. Right ascension is usually given in combination with declination.
Used together with declination, it is one of the coordinates used to reference celestial objects and is equivalent to a longitude reference on the Earth. There are 24 hours of right ascension within 360 degrees, so one hour is equivalent to 15 degrees.
The compass bearing of an object in the sky
One of the celestial coordinates, right ascension (or RA) measures distance around the ecliptic.
a celestial coordinate; it is the angular distance measured from the vernal equinox eastward along the celestial equator to the hour circle of a given star or other celestial body. It can be defined also as the arc of the celestial equator or the angle at the celestial pole between the hour circle of the vernal equinox and the hour circle of the body.
(RA): position on the celestial sphere measured with respect to the vernal equinox position on the celestial equator. It is a projection of longitude lines onto the sky and converted to time units. An object's right ascension is fixed with respect to the stars. Varies from 0h at the vernal equinox point to 24h in a full circle.
Celestial coordinate used to measure longitude on the celestial sphere. The zero point is the position of the Sun on the vernal equinox.
The celestial equivalent of Earth's longitude, beginning at a line running pole to pole and cutting through eastern Pegasus. In meteor astronomy the right ascension is handled in degrees, starting at zero degrees and advancing eastward around the sky for a full 360 degrees ending in eastern Pegasus. For the rest of astronomy, the right ascension is handled as a time measurement. Since it takes 24 hours for the Earth to rotate, the sky is divided into 24 one hour wide bands. Each hour of right ascension equals 15 degrees.
(astronomy) the angular distance eastward along the celestial equator from the vernal equinox to the intersection of the hour circle that passes through the body; expressed in hours and minutes and second; used with declination to specify positions on the celestial sphere; "one hour of right ascension equals fifteen degrees"
an arc of the celestial equator eastward from the vernal equinox
A coordinate for measuring the east-west positions of celestial bodies; the angle measured eastward along the celestial equator from the vernal equinox to the hour circle passing through a body.
The angle, measured eastward on the celestial equator, between the First Point of Aries and the hour circle through the object.
An angular measurement of a point on the celestial sphere, corresponding to an angle before or after the vernal equinox line. Roughly equivalent to longitude in terrestrial measures, except that right ascension is given in hours, minutes, and seconds rather than in degrees, minutes, and seconds. Complement to declination.
(RA). Hour angle between first Point of Aries and the hour circle through a body, measured easterly through 360 degrees and converted to time.
Analogous to lines of longitude, Right Ascension is divided into 24 hours increasing from east to west. Facing north, objects appear to rise on your right (east), hence the name Right Ascension. back to the top
The celestial equivalent to lines of longitude, which runs through the celestial poles and are perpendicular to the celestial equator; they are scaled in hours, increasing eastward from 0h and going full circle to 24h
along with declination, a means of defining the position of objects in space, referred to a known point. Similar to the angular system used to define latitude and longitude on Earth's surface, right ascension is roughly analogous to longitude, and defines an angular offset from the meridian of the vernal equinox. See Celestial Sphere Figure.
The equatorial coordinate specifying the angle (usually specified in hours, minutes and seconds), measured eastward along the celestial equator from the vernal equinox to the hour circle passing through an object in the sky.
the angular distance around the sky parallel to the celestial equator; measured in hours h, minutes m and seconds s
The positions of stars and planets on the celestial sphere can be plotted using right ascension and declination or dec. These are the equivalent to latitude and longitude on Earth. Right ascension is measured in hours minutes and seconds, either East or West, from the point where the ecliptic crosses the celestial equator at the vernal equinox. If an object has an R.A. of two hours West it will rise two hours after the vernal equinox. Stars always have the same R.A. and dec, because they do not move on the celestial sphere. Planets however are always moving and their position has to be checked regularly by observers.
celestial coordinate used to measure "longitude" on the celestial sphere; zero point is position of the Sun as it crosses the celestial equator
The coordinate on the sky analogous to longitude on Earth, measured around the celestial equator from a specific place in the sky known as the vernal equinox.
The analog, on the celestial sphere, of the longitude circles on Earth.
( - alpha) Equivalent to Longitude. Instead of being divided into 360 degrees as on Earth, Right Ascension is noted in Hours, Minutes & Seconds. There are 24 Hours each equal to 15 degrees (24 hrs. x 15 deg. = 360 deg. - get it) starting at a 0 (zero) hour meridian to 23 hours. Each hour is divided into 60 minutes and each minute is divided into 60 seconds. For example the cooridinates (position) for a certain star can be expressed as a Right Ascension of 12h25m13s. This locates the position along the Celestial Equator and is used in conjuction with the Declination to define the exact location on the Celestial Sphere. An example of a complete set of coordinates (RA & Dec.) is 12h25m13s-42d14m37s. Also see Declination.
n the equatorial co-ordinate system, the angular distance of an object eastward from the zero point (which is the vernal equinox), usually expressed in hours and minutes (which represents Earth's rotation from the vernal equinox to the object). It is the celestial equivalent of longitude on Earth's surface.
the angle of a celestial object from the vernal equinox, measured eastward along the celestial equator. The angle is generally expressed in hours, minutes and seconds.
(RA) See Equatorial coordinates.
With declination, one of the coordinates used to designate the location of an object on the celestial sphere. Right ascension is measured in hours, minutes, and seconds and is similar to longitude on Earth.
On of the coordinates used to define position on the celestial sphere in the equatorial coordinate system. It is equivalent of longitude on the Earth but is measured in hours, minutes and seconds of time eastwards from the zero point, which is taken as the intersection of the celestial equator and the ecliptic, know as the first point of Aries.
The angular distance, measured Eastwards, from the Vernal Equinox. It is one of the ordinates used to reference objects on the celestial sphere. It is the equivalent to a longitude reference on the Earth. There are 24 hours of right ascension within 360 degrees, so one hour is equivalent to 15 degrees. Together with declination, it represents the most commonly used co-ordinate system in modern astronomy.
the angular distance of a celestial object east of the vernal equinox; the celestial sphere equivalent of longitude
The amount of time that passes between the rising of Aries and another celestial object. Right ascension is one unit of measure for locating an object in the sky.
One of two coordinates (see also: declination) used to define the position of an object on the sky. Right ascension (R.A.) is the angular distance of the object eastward from the vernal equinox, measured not in degrees but in terms of time: hours minutes and seconds. (1 hour = 15 arc degrees.) Equivalent to terrestrial longitude, with the vernal equinox playing the role of the Greenwich meridian.
angle parallel to the celestial equator, measured eastwards from the spring equinox.
angular distance east of the vernal equinox, as measured on the celestial equator.
Measurement along the celestial equator eastward from 0° Aries that describes planetary positions in terms of degrees, minutes and seconds, not zodiacal signs. Sidereal time expressed in unit of arc.
A coordinate used by astronomers to locate stars and other celestial objects in the sky. Right ascension is comparable to longitude, but it is measured in hours, minutes, and seconds because the entire sky appears to pass overhead over a period of 24 hours. The zero hour corresponds to the apparent location of the Sun with respect to the stars on the day of the vernal (spring) equinox (approximately March 21).
Measurement along the equator by degrees only from the first point of Aries. 360 degrees into 24 hours means each degree occupies about 4 minutes (of clock time) on the equator.
Right ascension is a celestial coordinate that is used to measure the degrees of longitude on the on the celestial sphere. Zero degrees of right ascension is the position of the Sun during the vernal (spring) equinox (March 21).
Right ascension (abbrev. RA; symbol α), also known as celestial longitude, is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. The other coordinate is the declination.