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Topic: Hipparchus (astronomer)

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	Hipparchus (astronomer) Encyclopedia
		Hipparchus is believed to have died on the island of Rhodes, where he spent most of his later life -- Ptolemy attributes observations made on Rhodes in the period from 141 BC to 127 BC to Hipparchus.
		Hipparchus was the first to show that the stereographic projection is conformal, and that it transforms circles on the sphere that do not pass through the center of projection to circles on the plane.
		Hipparchus ranked stars in six magnitude classes according to their brightness: he assigned the value of one to the twenty brightest stars, to weaker ones a value of two, and so forth to the stars with a class of six, which can be barely seen with the naked eye.
	www.hallencyclopedia.com /topic/Hipparchus_(astronomer).html (0 words)

	Hipparchus the Astronomer
		Hipparchus discovered the precession of the equinoxes and was influential in the development of trigonometry, redefined and formalized the projection as a method for solving complex astronomical problems without spherical trigonometry and probably proved its main characteristics.
		Hipparchus determined the distance from the Earth to the Moon from observations of a solar eclipse in Syene and in Alexandria.
		Hipparchus, according to Ptolemy, considered that the Earth is not the center of the circular orbit of the Sun.
	www.mlahanas.de /Greeks/Hipparchus.htm (0 words)

	Hipparchus
		Hipparchus had been stimulated in 134 BC by observing a "new star." Concluding that such a phenomenon indicated a lack of permanency in the number of "fixed" stars, he determined to catalog them, and no criticism was able to deflect him from his original purpose.
		Hipparchus satisfactorily accounted for that inequality of the Moon's motion that is now known to be due to the elliptical form of its orbit; he utilized the system of circular epicycles and deferent but proposed that the deferent was inclined at an angle of 5 to the ecliptic.
		Hipparchus followed the method used by Aristarchus, a procedure that depends upon measuring the breadth of the Earth's shadow at the distance of the Moon (the measurement being made by timing the transit of the shadow across the Moon's disk during a lunar eclipse).
	abyss.uoregon.edu /~js/glossary/hipparchus.html (1752 words)

	Hipparchus - MSN Encarta
		Hipparchus was born in Nicaea, Bithynia (now İznik, Turkey).
		Hipparchus devised a method of locating geographic positions by means of latitudes and longitudes.
		Hipparchus also compiled a table of trigonometric chords that became the basis for modern trigonometry.
	uk.encarta.msn.com /encyclopedia_761555438/Hipparchus.html (132 words)

	Hipparchus biography
		Since when Ptolemy refers to results of Hipparchus he does so often in an obscure way, at least he seems to assume that the reader will have access to the original writings by Hipparchus, and it is certainly surprising that neither Theon or Pappus fills in the details.
		Hipparchus appears to know that 67 earth radii for the distance of the moon comes from this upper limit of solar parallax, while the lower value of 59 earth radii corresponds to the sun being at infinity.
		Hipparchus was also able to give an epicycle model for the motion of the sun (which is easier), but he did not attempt to give an epicycle model for the motion of the planets.
	www-history.mcs.st-andrews.ac.uk /Biographies/Hipparchus.html (0 words)

	Hipparchus Biography
		That Hipparchus continued to be held in high regard is demonstrated by the various depictions of him on frontispieces of astronomical works published long after his death.
		But Hipparchus did compile the planetary observations to which he had access into a more useful arrangement, and demonstrated that the phenomena were 'not in agreement with the hyotheses of the astronomers of that time'.
		Hipparchus' discussion of the motion of the points of solstice and equinox slowly from east to west against the background of the fixed stars is perhaps his most famous achievement; he has been therefore credited with the discovery of the precession of the equinoxes.
	www.hps.cam.ac.uk /starry/hipparchus.html (0 words)

	Ancient Astronomy
		Hipparchus never confirmed whether the bright light he saw was truly a new star.
		While Asian astronomers were making careful observations, European astronomy had degenerated into primitive notions of astrology, treating anything and everything in the sky as omens of disaster.
		Since astronomical events were treated as omens of disaster, Marschall argues, perhaps the summer of 1054 wasn't the best time to be recording unusual new stars.
	snews.bnl.gov /popsci/ancients.html (1161 words)

	Hipparchus, Greek astronomer — FactMonster.com
		Ptolemy's geocentric theory of the universe was based largely on the conclusions of Hipparchus, a record of whose researches is preserved in the
		In it Hipparchus is credited with the discovery of the precession of the equinoxes, the eccentricity of the sun's apparent orbit, and certain inequalities of the motions of the moon.
		Hipparchus suggested a method of determining longitude by observing the parallax of the moon in eclipse.
	www.factmonster.com /ce6/people/A0823774.html (0 words)

	Mathematicians - Timeline Index
		Hipparchus was the most important Greek astronomers of his time.
		Nicolaus Copernicus was an astronomer who provided the first modern formulation of a heliocentric (sun-centered) theory of the solar system in his epochal book, De revolu...
		John Dee was a noted British mathematician, astronomer, astrologer, geographer, and consultant to Queen Elizabeth I. He also devoted much of his life to alchemy, divinati...
	www.timelineindex.com /content/select/1495 (0 words)

	Ian Ridpath’s Star Tales
		At its heart was a catalogue of 1022 stars arranged into 48 constellations (see Table 1), with estimates of their brightness, based largely on the observations of the Greek astronomer Hipparchus three centuries earlier.
		Ptolemy did not identify the stars in his catalogue by means of Greek letters, as astronomers do today, but described their position within each constellation figure.
		As well as a translation of Ptolemy’s catalogue, this book contained a listing of the Arabs’ own star names, magnitudes determined by al-Sufi himself, and two drawings of each constellation, one as it is seen in the sky and one reversed right to left as it would appear on a celestial globe.
	www.ianridpath.com /startales/startales1b.htm (0 words)

	The Definition of the Babylonian Zodiac and the Influence of Babylonian Astronomy on the Subsequent Defining of the ...
		Thus the first astronomical coordinate system came into being, through which the positions of the stars and planets along the ecliptic could be determined between 0° and 30° within the twelve zodiacal signs.
		In the last analysis this thesis pays tribute to those early astronomers who kept records of their observations and were able on this basis to arrive at the innovation of the ecliptic coordinate system of the zodiac, which was central to the whole subsequent development of astronomy as a science.
		In contrast, according to Hipparchus the Greek astronomer Eudoxus (fourth century B.C.) defined the vernal and autumnal points to be at 15° Aries and 15° Libra and the summer and winter solstitial points to be at 15° Cancer and 15° Capricorn.
	www.astrologer.com /aanet/pub/transit/jan2005/babylonian.htm (1901 words)

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