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right ascension

(direction coordinate along celestial equator)

Right ascension is the distance to an hour circle as an angle measured along the celestial equator eastward from the vernal equinox. It and declination together specify a direction, i.e., a point in the celestial sphere. Declination and right ascension are analogous to latitude and longitude, respectively.

Right ascension (but not declination) is commonly cited in angular hours, which equal 15 degrees, i.e., the angular distance the Earth rotates in an hour. The hours are subdivided into minutes and seconds that are 1/60 and 1/3600 of an angular hour, rather than of a degree. But right ascension also may be cited in degrees.

Hour angle is another type of measure of the placement of an hour circle: there is more than one kind of hour angle, but a common type counts hours from the observer, and westward, i.e., the opposite direction around Earth as does right ascension.

(coordinate,equatorial,celestial sphere,measure)

Referenced by:
AD Leonis (AD Leo)
Algol (Beta Per)
Alpha Centauri
arcsecond (arcsec)
AU Microscopii (AU Mic)
Baade's Window
Barnard's Star
Beta Centauri
Canis Major Dwarf Galaxy
celestial sphere
Circinus Galaxy (ESO 97-G13)
declination (dec)
Extended Groth Strip (EGS)
Elias 2-27
Epsilon Eridani
Epsilon Indi (ε Indi)
equatorial coordinate system
ESO 137-001
galactic north
GG Tau
Hubble Deep Field (HDF)
Hubble Deep Field South (HDF-S)
HL Tau
HR 8799
Hubble Ultra-Deep Field (HUDF)
J2000.0 equinox
J designator
Kapteyn's Star
Kepler Telescope
Lacaille 9352
Lalande 21185
LHS 1140
Large Magellanic Cloud (LMC)
Lockman hole
Luhman 16
Luyten 726-8
Crab Nebula (M1)
Andromeda (M31)
Triangulum Galaxy (M33)
NGC 1600
NGC 253
NGC 2770
NGC 3314
Ohio Radio Survey
Hulse-Taylor Binary (PSR B1913+16)
Rho Ophiuchi Cloud Complex
Ross 154
Ross 248
Sagittarius Dwarf Irregular Galaxy (SagDIG)
Sagittarius Dwarf Elliptical Galaxy (Sgr dE)
Scholz's Star
Small Magellanic Cloud (SMC)
solar apex
3C 273
3C 295
3C 48
Taurus Molecular Cloud 1 (TMC-1)
T Tauri
TW Hydrae (TW Hya)
Ursa Major II Dwarf
WISE 0855-0714
WISE 1506+7027
Wolf 359