In our own modern times the struggle for the correct data to calculate the horoscope is in the distant past. We are fortunate to have the conveniences of a highly accurate ephemeris based on modern astronomical methods, convenient tables of houses and accurate geographical information to determine location. Now with the advent of digital technology we can have the horoscope literally at our fingertips. This is all well and good, but it comes with a price. This overwhelming flood of information has a tendency to move us toward one of the big problems of the modern age-an over reliance on quantitative method. Quantitative methods have a very important part to play in our art, but they should not overshadow the human imagination which is the the real goal of the astrologer.
For most of us who live in urban areas the sky is not that important. We are indoors quite a lot, and even when we are outside, the architectural landscape, electric lights and pollution obscures our vision. When we are away from all the clutter while on a camping trip or a cruise at sea the appearance of the sky is a splendid thing that cannot be ignored. As we look up it seems as if we are underneath a large bowl with the celestial objects on its surface. This bowl is the upper half of the celestial sphere. The lower half is directly beneath us below the earth. Even though we all know that the earth revolves around the sun and the sun revolves around the galaxy and all the galaxies are in motion, it is this first sensible impression of us in the center and the sphere of infinite radius beyond that we must remember. This is the geocentric basis of Claudius Ptolemy's astronomy and the bedrock of astrology.
THE EARTH AND ITS MOTIONS
AS ABOVE SO BELOW
THE HORIZON SYSTEM
THE EQUATORIAL SYSTEM
THE ECLIPTIC SYSTEM
Introduction
In ancient times knowledge of the celestial sphere was a prerequisite for the study of astrology. The astrologer was usually only equipped with an ephemeris. The houses were calculated by a time consuming process of trigonometric formulas. Even the latitude and longitude of the chart were major questions. The advent of pre-calculated tables of houses in the medieval period and the geographic research and explorations of the early modern period were tremendous advances which led to the flowering of astrology in the renaissance. Yet even with an accurate ephemeris, a table of houses and a modern gazette knowledge of the celestial sphere was still a prerequisite. The calculation was complicated and filled with many steps each of which was subject to error. To guard against the wrong result, the experienced astrologer knew the workings of the sky and had a quick understanding of how the chart should look based on the knowledge of the celestial sphere. The ancients and our early modern forebears also considered this knowledge of the celestial sphere in a larger qualitative sense. This was the understanding that astrology is an art of the imagination and that the primary image of astrology is the celestial sphere. The meaning of the horizon and the meridian, the sun and the moon and the planets and stars and eventually the zodiac take on a far greater significance when they are known in their primary natural state as sensible objects with specific appearances and periods.
The sphere of the earth rotates on its axis once a day through the 24 hour period which is the quickest and most important celestial motion we experience. This eastward rotation causes the sun, moon and stars to appear on the eastern horizon, rise to the upper meridian and set on the western horizon. This movement is called diurnal motion. Through the year we experience seasons which are caused by the revolution of the earth around the sun and the tilt of the earth's axis to its path around the sun. On the first day of spring the sun appears on the equator this is where the sun occupies the first point of Aries. Through the year the sun continues to its greatest distance north of the equator at the summer solstice or the first point of cancer, then back to the equator at the autumnal equinox or the first point of Libra and then it recedes to its greatest distance south at the winter solstice or the first point of Capricorn.
To more clearly understand the celestial sphere we should remember our basic geography. The earth is a sphere with a north and south pole and an equator. Terrestrial latitude is measured along a meridian from the equator through 90 degrees to either the north or south pole. Terrestrial longitude is measured along the equator or a parallel of latitude from the prime meridian east or west through 180 degrees.
Similarly, the three reference systems of the celestial sphere use the same rectangular coordinate system as latitude and longitude on earth. These coordinate systems are the horizon system, the equatorial system and the ecliptic system. Each of these systems is a projection from the center of the earth to the infinite radius of the celestial sphere. All three views are similar, only their reference planes are different. The horizon system uses the celestial horizon as its reference plane. The equatorial system uses the celestial equator as its reference plane and the ecliptic system uses the ecliptic (the path of the sun) as its reference plane. All three of these reference planes are called great circles. A great circle is a circle the plane of which passes through the center of the earth. A small circle does not pass through the center of the earth. Examples of great circles are the equator and the meridian. An example of a small circle is a parallel of latitude.
The horizon system is the easiest to understand. The reference plane of the horizon system is the observer's celestial horizon. The celestial horizon is a projection of the observer's horizon onto the celestial sphere. From the observer's view the point directly overhead is the zenith which is similar to the terrestrial north pole. The point directly below is the nadir which is similar to the terrestrial south pole. Midway between the zenith and nadir lies the horizon which corresponds to the terrestrial equator. Angular distance above the horizon is called altitude and is measured along a vertical circle from the horizon through 90 degrees to the zenith. Altitude is similar to terrestrial latitude. Angular distance along the horizon is called azimuth angle and is measured along the horizon from the north to the south through 180 degrees on either side of the north-south line. Azimuth angle is similar to terrestrial longitude.
The reference plane of the equatorial system is the celestial equator. The celestial equator is a projection of the earth's equator onto the celestial sphere. Here the correspondence between the celestial sphere and the terrestrial sphere is exact. The north pole becomes the north celestial pole, the south pole becomes the south celestial pole and the equator becomes the celestial equator. Angular distance north or south of the celestial equator is called declination and is measured along a celestial meridian through 90 degrees toward the north or south celestial poles. Angular distance along the celestial equator is called right ascension and is measured from the first point of aries eastward along the celestial equator through 360 degrees.
The reference plane of the ecliptic system is the Ecliptic. The ecliptic is a great circle composed of the apparent path of the sun and the center of the earth. Angular distance north or south of the ecliptic is known as celestial latitude and is measured along a meridian of celestial longitude through 90 degrees to either the north or south poles of the ecliptic. Angular distance along the ecliptic is known as celestial longitude and is measured from the first point of Aries eastward through 360 degrees. Thus 0 degrees Aries equals 0 degrees longitude, 0 degrees cancer equals 90 degrees longitude and so on through 29 degrees Pisces which equals 359 degrees longitude.
End of Part 1