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The ascendant ( or As), or rising sign, is the zodiacal sign and degree that was ascending on the eastern horizon at the specific time and location of an event. According to astrological theory, celestial phenomena reflect or determine human activity on the principle of 'as above so below'. Thus astrologers believe that the ascendant signifies a person's awakening consciousness, in the same way that the Sun's appearance on the eastern horizon signifies the dawn of a new day.〔Jeff Mayo, ''Teach Yourself Astrology'', p71, Hodder & Stoughton, London, 1991〕 Because the ascendant is specific to a particular time and place, to astrologers it signifies the individual environment and conditioning that a person receives during their upbringing, and also the circumstances of their childhood.〔Sasha Fenton, ''Rising Signs'', pp 13-14, The Aquarian Press, London, 1989〕 For this reason astrologers believe that the ascendant is also concerned with how a person has learned to present themself to the world, especially in public and in impersonal situations. To astrologers, in some circumstances, it can function as a shield or mask to guard a person's real nature - in other words the 'defense mechanism' every person has to cope with unfamiliar or uncomfortable situations. Astrologers believe the ascendant also has a strong bearing on a person's physical appearance and overall health. The Ascendant is thus considered to be of great significance in all schools of astrology because it in effect serves as the filter through which everything in a horoscope- including the Sun and Moon- is expressed. Most astrologers believe that the Rising Sign exerts an influence equal to or more powerful than the Sun and Moon. In Jyotish, the ascendant is without question the most individual and defining element in the chart. ==Calculation== The Ascendant, from an astronomical point of view, is the value of the ecliptical geocentric longitude (aka Celestial Longitude λ) of the point of the ecliptic which is easterly on the horizon. 〔Jean Meeus, ''Astronomical Algorithms'', p99, 1991〕 where A is the local sidereal time in degrees, E is the inclination of Earth's equatorial plane to the ecliptic or obliquity of the ecliptic. For values referred to the standard equinox J2000.0 use 23.4392911°, for J1950.0 use 23.4457889°. L is the local latitude (Southern latitudes are negative, Northern positive). The Ascendant is then found in the correct quadrant (0 to 360 degrees) by using the two rules:〔Peter Duffett-Smith, Jonathan Zwart, ''Practical astronomy with your calculator or spreadsheet-4th ed.'', p47, 2011〕 If (x < 0) then Ascendant = Ascendant + 180 else Ascendant = Ascendant + 360 By definition of Ascendant, we have to take the point easterly (the rising one) by using a final rule: if (Ascendant < 180) then Ascendant = Ascendant + 180 else Ascendant = Ascendant - 180 Otherwise a direct result in the correct quadrant can be determined if calculator or programming software has the atan2(y,x) math function and then using the last rule. ==Long and short ascension== Because the Earth's axis (see axial tilt) is tilted relative to the ecliptic, the twelve signs do not take the same amount of time to cross the eastern horizon. At the equator, there is very little difference (Pisces, Aries, Virgo and Libra take slightly less time than the other signs) but as one moves from the equator, larger and larger differences emerge. In the northern hemisphere, the signs of Aquarius, Pisces, Aries, Taurus and Gemini take much less time than the theoretical two hours to cross the eastern horizon, whilst the signs of Cancer, Leo, Virgo, Libra, Scorpio and Sagittarius take much longer than two hours to do so. For example, at the latitude of Paris, France: * Pisces, Aries, Aquarius and Taurus take only about forty-four minutes to cross the eastern horizon (this is referred to as the ''length of ascension'' or simply as the sign's ''ascension'') * Capricorn and Gemini have an ascension of only about seventy minutes * Cancer and Sagittarius have an ascension of around two and a half hours * Leo, Virgo, Libra and Scorpio have ascensions of around two hours and forty-five minutes At higher latitudes, these differences become even more marked. At the latitude of St. Petersburg, Russia: * Pisces and Aries ascend in only ''thirty minutes'' * Aquarius and Taurus ascend in only ''forty-five minutes'' * Capricorn and Gemini ascend in an hour and a half * * actually individual degrees near Sagittarius or Cancer ascend twice as slowly as those near Aquarius or Taurus * Sagittarius and Cancer ascend in two hours and forty minutes * Leo, Virgo, Libra and Scorpio take as much as three hours and fifteen minutes to ascend Astrologers consider the differences between the rate at which the signs ascend to be of importance. In many house systems, houses can become very large when they cover Aquarius, Pisces, Aries and Taurus because these signs are seen to be much smaller from the perspective of a northern hemisphere observer. Some astrologers, such as Richard Nolle, consider the preponderance of Ascendants in signs from Cancer through Sagittarius (known as the ''western signs'') to be symbolic of the highly relationship-oriented character inherent in a complex or civilized society as found today in the northern hemisphere but never developed in equatorial or south temperate latitudes where ''eastern'' (Capricorn through Gemini), individual-oriented Ascendants are equally or more common.〔Richard Nolle, "Chiron: New Planet in the Horoscope", pages 78 to 82〕 In the southern hemisphere, long and short ascension are reversed. For instance, at the latitude of Concepción, Chile: * Pisces and Aries ascend in two hours twenty minutes * Aquarius and Taurus ascend in two and a half hours (see note about ascension in low latitudes above) * Capricorn and Gemini ascend in two hours twenty minutes * Sagittarius and Cancer ascend in almost exactly two hours * Scorpio and Leo ascend in about ninety minutes * Libra and Virgo ascend in about seventy-five minutes 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ascendant」の詳細全文を読む スポンサード リンク
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