The invention provides a zodiac sign horoscope mapping device, locating the coordinate positions of the twelve zodiac signs, in a manner accurately reflecting the precession of the equinoxes. The device divides the ecliptic coordinate sphere into twelve uniform longitudinal arcs, aligning an origin by a zodiac sign to degree, and thereby locating the twelve zodiac signs along the sphere. A dependent device divides the ecliptic coordinate sphere into twelve non-uniform arcs, each arc isomorphic to the longitudinal span of one of the twelve traditional zodiac constellations, and thereby locating each zodiac sign as isomorphic to its named constellation. The invention provides an astrological horoscope device, which provides the calendar dates of the year for each zodiac Sun sign. The invention provides a horoscope generating method, which can comprise a horoscope computer program's functional specification. The invention provides a horoscope generating computer program.