The horoscope serves as a stylized map of the heavens over a specific location at a particular moment in time. In most applications the perspective is geocentric (heliocentric astrology being one exception). The positions of the actual planets (including Sun and Moon) are placed in the chart, along with those of purely calculated factors such as the lunar nodes, the house cusps including the midheaven and the ascendant, zodiac signs, fixed stars and the lots. Angular relationships between the planets themselves and other points, called aspects, are typically determined. The emphasis and interpretation of these factors vary with tradition. This means however the stars were placed at the time of birth for a person shows their characteristics and personality, including weakness.
Concepts in the Western astrology
- The native is the subject of the event (a birth, for example) being charted at a particular time and place, and is considered to be at the center of the celestial sphere.
- The celestial sphere is an imaginary sphere onto which the zodiac, constellations, and planets are projected.
- The plane of the equator is the plane of the Earth’s equator projected into space.
- The plane of the ecliptic is defined by the orbits of the earth and the sun. For practical purposes, the plane of the equator and the plane of the ecliptic maintain a constant inclination to each other of approximately 23.5°.
- The plane of the horizon is centered on the native and is tangential to the earth at that point. In a sphere whose radius is infinitely large, this plane may be treated as nearly equivalent to the parallel plane with its center at the Earth’s center. This greatly simplifies the geometry of the horoscope but does not take into account that the native is in motion. Some writers on astrology have thus considered the effects of parallax, but most would agree that (apart from that of the moon) they are relatively minor.
To complete the horoscope the astrologer will consider the aspects or relative angles between pairs of planets. More exact aspects are considered more important. The difference between the exact aspect and the actual aspect is called the orb. Those generally recognized by the astrological community are Conjunction (0°), Opposition (180°), Square (90°), Trine (120°), Sextile (60°), Semi-Square (45°), Sesquisquare (135°), and Quincunx (150°). Understandably these aspects are more significant when they are exact, but they are considered to function within an orb of influence, the size of which varies according to the importance of each aspect. Thus conjunctions are believed to operate with a larger orb than sextiles. Most modern astrologers use an orb of 8° or less for aspects involving the Sun, Moon, and Jupiter and smaller orbs for the other points. Some astrologers, such as practitioners of Cosmobiology, and Uranian astrology, use minor aspects (15°, 22.5°, 67.5°, 72°, 75°, 105°, 112.5°, 157.5°, 165°) with much narrower orbs.
The major astrological system regarded universally is Vedic Hindu Astrology. As per this, all planets see just an opposite i.e. 180-degree aspect. But Mars, Jupiter, and Saturn have special aspects. Mars sees the houses 4th and 8 too from its place in the horoscope, Saturn sees the houses 3 and 10 too from its place, and Jupiter sees 5 and 9 from its place in the horoscope i.e. the house in which they are posited in the Lagna chart.