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.
AD Leonis (AD Leo)
Algol (Beta Per)
Canis Major Dwarf Galaxy
Circinus Galaxy (ESO 97-G13)
Extended Groth Strip (EGS)
Epsilon Indi (ε Indi)
Equatorial Coordinate System
Hubble Deep Field (HDF)
Hubble Deep Field South (HDF-S)
Hubble Ultra-Deep Field (HUDF)
Large Magellanic Cloud (LMC)
Crab Nebula (M1)
Triangulum Galaxy (M33)
Hulse-Taylor Binary (PSR B1913+16)
Rho Ophiuchi Cloud Complex
Sagittarius Dwarf Irregular Galaxy (SagDIG)
Sagittarius Dwarf Elliptical Galaxy (Sgr dE)
Small Magellanic Cloud (SMC)
Taurus Molecular Cloud 1 (TMC-1)
Ursa Major II Dwarf