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Right ascension and declination as seen on the inside of the celestial sphere. The primary direction of the system is the March equinox, the ascending node of the ecliptic (red) on the celestial equator (blue). Right ascension is measured eastward up to 24 h along the celestial equator from the primary direction.
Declination (vertical arcs, degrees) and hour angle (horizontal arcs, hours) is shown. For hour angle, right ascension (horizontal arcs, degrees) can be used as an alternative. The equatorial coordinate system is a celestial coordinate system widely used to specify the positions of celestial objects.
Right ascension and declination as seen on the inside of the celestial sphere. The primary direction of the system is the vernal equinox, the ascending node of the ecliptic (red) on the celestial equator (blue). Declination is measured northward or southward from the celestial equator, along the hour circle passing through the point in question.
Right ascension: Declination: Constellation: North Pole +90° latitude 12 h 51.4 m +27.13° Coma Berenices (near 31 Com) South Pole −90° latitude 0 h 51.4 m: −27.13° Sculptor (near NGC 288) Center 0° longitude 17 h 45.6 m: −28.94° Sagittarius (in Sagittarius A) Anticenter 180° longitude 5 h 45.6 m +28.94° Auriga (near HIP 27180)
Like right ascension in the equatorial coordinate system, the primary direction (0° ecliptic longitude) points from the Earth towards the Sun at the March equinox. Because it is a right-handed system, ecliptic longitude is measured positive eastwards in the fundamental plane (the ecliptic) from 0° to 360°.
For example, when the Sun is at an elevation of 10°, it appears to be at 10.1°. The Sun's declination can be used, along with its right ascension, to calculate its azimuth and also its true elevation, which can then be corrected for refraction to give its apparent position.
In contemporary astronomy, 88 constellations are recognized by the International Astronomical Union (IAU). [1] Each constellation is a region of the sky bordered by arcs of right ascension and declination, together covering the entire celestial sphere.
Right Ascension Declination Distance (Light-years) Apparent Absolute; Sun: G2V −26.74 4.80 — — 0 α Centauri: A G2V −0.01 4.34 14 h 39 m 36.50 s: −60° 50′ 02.3″ 4.34 B K1V 1.35 5.71 14 h 39 m 35.08 s: −60° 50′ 13.8″ Sirius (α Canis Majoris) A1V −1.44 1.45 06 h 45 m 08.92 s: −16° 42′ 58.0″ 8.60 ε Eridani: K2V 3. ...
Right ascension: 02 h 31 m 49.09 s: Declination +89° 15′ 50.8″ Apparent magnitude (V) 1.98 (1.86 – 2.13) α UMi B: Right ascension: 02 h 30 m 41.63 s: Declination +89° 15′ 38.1″ Apparent magnitude (V) 8.7: Characteristics α UMi A Spectral type: F7Ib: U−B color index: 0.38: B−V color index: 0.60: Variable type: Classical Cepheid
Coordinates. Accurate planispheres represent the celestial coordinates: right ascension and declination. The changing positions of planets, asteroids or comets in terms of these coordinates can be looked up in annual astronomical guides, and these enable planisphere users to find them in the sky.
