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  2. Polar distance (astronomy) - Wikipedia

    en.wikipedia.org/wiki/Polar_distance_(astronomy)

    An object on the celestial equator has a PD of 90°. Polar distance is affected by the precession of the equinoxes. If the polar distance of the Sun is equal to the observer's latitude, the shadow path of a gnomon's tip on a sundial will be a parabola; at higher latitudes it will be an ellipse and lower, a hyperbola.

  3. Ecliptic coordinate system - Wikipedia

    en.wikipedia.org/wiki/Ecliptic_coordinate_system

    Ecliptic latitude or celestial latitude (symbols: heliocentric b, geocentric β), measures the angular distance of an object from the ecliptic towards the north (positive) or south (negative) ecliptic pole. For example, the north ecliptic pole has a celestial latitude of +90°. Ecliptic latitude for "fixed stars" is not affected by precession ...

  4. Celestial equator - Wikipedia

    en.wikipedia.org/wiki/Celestial_equator

    In other words, the celestial equator is an abstract projection of the terrestrial equator into outer space. [1] Due to Earth's axial tilt , the celestial equator is currently inclined by about 23.44° with respect to the ecliptic (the plane of Earth's orbit ), but has varied from about 22.0° to 24.5° over the past 5 million years [ 2 ] due ...

  5. Astronomical coordinate systems - Wikipedia

    en.wikipedia.org/wiki/Astronomical_coordinate...

    The equatorial coordinate system is centered at Earth's center, but fixed relative to the celestial poles and the March equinox. The coordinates are based on the location of stars relative to Earth's equator if it were projected out to an infinite distance.

  6. Equatorial coordinate system - Wikipedia

    en.wikipedia.org/wiki/Equatorial_coordinate_system

    The right ascension symbol α, (lower case "alpha", abbreviated RA) measures the angular distance of an object eastward along the celestial equator from the March equinox to the hour circle passing through the object. The March equinox point is one of the two points where the ecliptic intersects the celestial equator.

  7. Position of the Sun - Wikipedia

    en.wikipedia.org/wiki/Position_of_the_Sun

    The Sun appears to move northward during the northern spring, crossing the celestial equator on the March equinox. Its declination reaches a maximum equal to the angle of Earth's axial tilt (23.44° or 23°26') [ 8 ] [ 9 ] on the June solstice , then decreases until reaching its minimum (−23.44° or -23°26') on the December solstice , when ...

  8. Earth-centered, Earth-fixed coordinate system - Wikipedia

    en.wikipedia.org/wiki/Earth-centered,_Earth...

    The plane of reference can be aligned with the Earth's celestial equator, the ecliptic, or the Milky Way's galactic equator. These 3D celestial coordinate systems add actual distance as the Z axis to the equatorial, ecliptic, and galactic coordinate systems used in spherical astronomy.

  9. Longitude by chronometer - Wikipedia

    en.wikipedia.org/wiki/Longitude_by_chronometer

    In order to calculate the position line, the time of the sight must be known so that the celestial position i.e. the Greenwich Hour Angle (Celestial Longitude - measured in a westerly direction from Greenwich) and Declination (Celestial Latitude - measured north or south of the equational or celestial equator), of the observed celestial body is ...