Home Discussion Forum What is the meaning of Right Ascension / Declination?

What is the meaning of Right Ascension / Declination?

I need a clear and comprehensive explanation please, thank you.


  1. it’s basically a latitude and longitude “mapping” of our sky.
    right ascension is the equivalent of longitude, but instead of using degrees, it is measured in Hours, Minutes, Seconds (etc.) to account for earth’s rotation.
    declination is the equivalent of latitude. and is measured in degrees, in fact, if an object has a declination that matches your latitude, when it crosses your meridian, it will be directly overhead.

  2. If you imagine the sky as the inside of a huge sphere, Rt. Asc is the equivalent of longitude lines going from the celestial north pole to the south. There are 24 hours of Rt. Asc., each hour equals 15 degress angle. Declination is the equivalent of latitudes, and the lines go east to west. The celestial north pole coincides with earth’s axis. The sidereal time ( star time ) is the Rt. Asc that’s over your head at any given time. 0 hours 0 minutes in Rt. Asc. is the First Point of Aries, which is where the sun crosses the celestial equator on the first day of Spring, just as the 0 degree earth longitude is the Prime Meridian of Greenwich England.


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