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Starting point of measurement 
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#1
Jul410, 05:07 PM

P: 367

Where is the starting point of measurement of the Ecliptic Longitude, the Ecliptic Latitude, Right Ascension, and Declination?



#2
Jul410, 10:09 PM

P: 61

Ecliptic Longitude: Is zero at the First Point of Aries, a line drawn on the plane of the ecliptic from the sun thru the earth as of the vernal equinox Ecliptic Latitude: Is zero along the plane of the ecliptic, the plane of Earth's orbit Right Ascension: Is zero at the ascending node, which for Earth only is also at the first point of Aries, also called the celestial meridian, where the plane of the ecliptic and the celestial plane  the plane perpendicular to the Earth spin axis  intersect at a line. For other planets, this zero point is set relative to Earth's zero point using the Right Ascension of Ascending Node Declination: I dunno. Please define. The line defining the first point of Aries actually traverses, as it were, around the zodiac in about 25000 years. It was zero and pointing at Aries in 70 BC (I looked that one up) but now it is pointing more towards Pisces. hth 


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