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RA and DEC are the coordinates on sky. RA (Right Ascension) is the angular position measured eastward in a full circle along the celestial equator. Dec (Declination) is the angular position measured from the celestial equator in either the north (positive) or south (negative) direction. $+90\,^{\circ}$ is the north celestial pole, $-90\,^{\circ}$ is the ...


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If you browse further down the page, there are details for each of the top table data. So RA and Dec give you coordinates (Right Ascension and Declination, like longitude and latitude). There is a designation J2000.0 which tells you the zero point to which the coordinates relate (remember, the Earth wobbles, so any coordinate system tied to Earth changes ...


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DEC :Declination RA :Right ascension Redshift / z :use to calculate velocity over earth z axis (azimuth) Magnitude/ Qual Filter : zoom into image filter quality (??) Separ arc min : if is a group as cloud magallans here more information


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I recently read the relevant parts of the Cambridge Concise History of Astronomy and I'd suggest it was partly good observation, partly luck. Good observation in that Thales would have noted that the movements of the Sun and Moon were such that eclipses were possible on certain dates, and luck in that the shadow of the eclipse he suggested was possible ...



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