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How does declination and right ascension relate to latitude / longetude?

  1. Aug 10, 2012 #1

    Sqw

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    It seems to me declination lines are vertical like longitude, and coordinates is measured horizontally (but if it runs vertical than how could it be measured as 0° at the equator?), and right ascension lines run horizontal like latitude with coordinates measured vertically.

    However this doesn't seem to be the case so I need some clarification.

    What directions do the declination and right ascension lines actually run? and where do their 0 degrees/hours begin?
     
  2. jcsd
  3. Aug 10, 2012 #2

    tiny-tim

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    Hi Sqw! :smile:

    No, declination (as the name suggests) is angle above the celestial equator, equivalent to latitude (and is 0 at the celestial equator), and right ascension (silly name) is equivalent to longitude (and is 0 at the vernal equinox), see http://en.wikipedia.org/wiki/Equatorial_coordinate_system :wink:
     
  4. Aug 16, 2012 #3
    Latitudinal Lines run North-South.

    Longitudinal Lines run West-East.

    They are fixed to the planet.

    Declination Lines run North-South but begin at the Ecliptic Plane but is fixed in the celestial Sky.

    The Ecliptic Plane varies depending what time of year it is will be -20 to 20deg from the Equator.

    Right Ascension run West-East on that plane also fixed in the sky and varies due to the time of day.
     
  5. Aug 17, 2012 #4

    davenn

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    you had better think about that one ;)

    lines of latitude run east west -- parallel to the equator :)

    and opposite for lines of longitude

    Dave
     
  6. Aug 17, 2012 #5
    I stand corrected.

    Longitudinal Lines do run from North-to-South. Increasing in magnitude from West-to-East. Are based on Terra Firma, Earth.

    Right Ascension Lines run from North-to-South. Increasing in magnitude from West-to-East. Are based on the Ecliptic Plane(the angle the Earth orbit makes with the Sun) and are fixed in the Sky. Right Ascension is based on the Longitude, the time of day, timezone, daylight savings time and the Local Mean Sidereal Time which equates it with the Vernal Equinox on the Ecliptic Plane.

    Latitudinal Lines do run from West-to-East. Increasing in magnitude from North-to-South. Are based on Terra Firma, Earth.

    Declination Lines run from West-to-East. Increasing in magnitude from North-to-South. Are fixed in the Sky. The magnitude is simply equal to the Latitude.
     
    Last edited: Aug 17, 2012
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