Astrology or some of its variations like numerology, palmistry, and Tarot card reading existed in almost all ancient civilizations. Whether it is believed to be a science or not, it has played a vital role and continues to play a vital role today. The main goal of Astrology is to attempt to identify positions and properties of various planets and their interaction with human behaviour. Astrology has a heavy scientific basis and to give an example it is a known fact that the moon is responsible for the high and low tides of the sea. It is also known that sun flares are responsible for electromagnetic radiation, which in turn affect communications. The word planetary positions, refers to astronomical properties like moons phases of brightness and the interaction of planets due to their proximity or opposition or their sensitive positioning at various points of the sky or Zodiac as is called in astronomical terms.
In-spite of their fair belief in astrology, many people don’t know how to use the astrological advice given in many magazines and newspapers. This is due to the fact that they are often given in terms that are foreign to readers such as, predictions based on position of sun at birth, position of moon at birth, and birth star. Another problem faced by many believers depends on the necessary calculations for persons born or residing at a place outside India. In these introductory articles, the different astrological data based on the birth particulars and their astronomical basis are explained.
Astrology consists of three parts, namely (a)Sidhdhanta or theoretical astronomical calculations for finding the planetary properties, (b) Predictive astrology which is based on birth data or in its absence by name by asking a prasna (question) and (c) Muhurta or to select an appropriate time to carry out an activity. In each of these specific parts there are many methods and techniques employed depending on the available data and an individual's own faith.
For example in the pre computer era, the theoretical calculations of planetary properties were determined by using old slokas based on classics like the “Surya Siddhanta”. However, the theory itself required many modifications due to astronomical events in the past which might have contributed to changes in the planetary positions and their properties. But with the availability of computers and their use for rocket and satellite launching, calculations of planetary positions at different places on earth have become a lot easier and accurate. This author had the privilege of being one of the earliest to develop such software to make all astronomical and astrological calculations required by Hindu system of astrology. Thus, using satellite launching tools, it has become incredibly easy to reduce calculation errors irrespective of the location on earth an individual is at. In fact, the same equations used in satellite launchings are incorporated by the author and many for astrological calculations. Thus modern tools have become handy to apply to an ancient branch of knowledge.
To appreciate and understand how to understand an astrological prediction, or to assess what birth data is really required for astrological analysis, a basic understanding of astronomy is essential. This ensures that the predictor does not become confused with the various systems and terms commonly used.
The planets (like Mercury, Venus, Mars, Jupiter, and Saturn) revolve around the sun with varying speeds and orbits. In turn, the planets have their own satellites. For example, Earth’s satellite is the Moon. Each of these celestial objects rotate around themselves which is referred to as the spin. For example, earth takes about 365.24 days to make a rotation around the sun – which is called the “Year”. The earth also spins around itself once in 24 hours called diurnal motion which causes day and night giving rise to day when its surface is exposed to sun and night when it is not exposed to sun. In contrast, the Moon takes about 28 days to complete one rotation around earth.
To give a nomenclature to different positions of the sky (Zodiac), some frame of reference is to be used. Thus, the sky is divided into 360 degrees – each portion identified by a star or stellar position. But the stars themselves or their parent group called “Galaxy” are moving with considerable speed.
These complex and quick motions make calculations of the position of any celestial body a meaningless and unreliable proposition. But as proposed in modern science: Theory of Relativity, ancient Hindu sages in astrology were aware of the fact that motion is absolutely relative – and without defining the positions of the observed, the data gathered will have no meaning. In the present context, there is no absolute “Frame of Reference, “ as the stellar and galactic system is constantly moving, and therefore there is no way to determine a planet’s position. It is like the Special theory of Relativity which states that no material object can reach the velocity of light. Thus, there is no way of measuring the absolute position of a celestial body as by the time an observation is made, the stellar system itself has moved. Astrological sages offered a great innovative solution to this problem by defining a theoretical or Fixed Zodiac. This system is popularly called Nirayana or the Indian System in contrast to Western system or Sayana or Moving zodiac system. In the Nirayana system the Zodiac or celestial circle is assumed to be fixed and correlates to the existing system thought to have existed during the original creation defined in Hindu mythology. Thus the stellar system or Zodiac starts with the Aswani star and is fixed irrespective of the time of birth.
In contrast, the Sayana system calculates based on the present position of the stellar system. This is due to the fact that the stellar system moves very little in a few days as compared to the planetary movements during the same period.
In addition to these complexities of motion, we have an additional problem: the “Inclined plane of rotation of earth around the sun”. This inclination is about 23.5 degrees and has a steady but great effect on the calculations. In-fact, it is this inclination that gives rise to the different seasons in a year. For the astronomical calculations this has a telling effect. To understand its effect, the North - South axis of earth is now pointing to the Polar star (or Dhruva Nakshatra of Hindu astronomy). But this axis moves with a steady but significant effect of about 55 seconds of angular arc. Thus, the present axis point of the pole star becomes Vega (of Alpha Lyra constellation of astronomy) once in 39000 years. It is this cyclic movement called precision which gives rise to the Sayana and Nirayana systems. This difference accumulated in the present cycle amounts to about 23.5 degrees of arc is the difference between Sayana and Nirayan Longitudes of planets.
Irrespective of the fixed (Nirayana) or moving (Sayana) system of zodiac, the zodiac or celestial cycle is divided into 360 degrees or 12 rasis or 27 stars. From caveman to modern man, the cycle or calendar in the year has a great effect on our daily life as seasons are controlled by the movement of sun and moon. The difference between 360 degrees movement of earth’s rotation around the sun in about 365.24 days gives rise to the Solar year and this difference of about 5.24 days is adjusted in different calendars by different methods. In the popularly used Gregorian calendar this discrepancy is adjusted by the leap year. It is worthwhile to note that the definition of leap year itself has undergone great changes. 10 days were dropped in the 14th century by Pope Gregory (hence the name Gregorian calendar ) by redefining leap year.
Irrespective of religious beliefs or civilizations the calendar reforms were a necessary part and have thus led to different calendars. Many social, religious, and festival activities (including agricultural activities which are dependent on seasons) are intricately linked with the calendar that is followed. The history and reforms in the calendar system is different and complesubject by itself.
It is the ingenuity of Hindu Sages that gave a permanent, everlasting, and self rectifying calendar. In the Nirayana system they followed, the Zodiac is defined into the following 12 rasis each encompassing 30 degrees . Each minute is subdivided into 30 minutes of arc and each minute into 30 seconds of arc.
The 12 signs are listed below with Indian and western(astronomical) names.
The movement of the sun to different rasis more or less occurs around a fixed date in the modified Gregorian calendar. But there is a difference of about 23 days (corresponding to the Ayanamsa of 23.5 degrees already mentioned) between the Nirayana and Sayana system.This movement of sun to different rasis is called solar ingress or Sankramanam . This is what causes seasonal changes and festivals. For example in the Christian calendar, while Christamas is on a fixed date of December 25th, Good Friday is related to the position of sun (in meena and mesha) and the position of moon (the occurrence of full moon day in chitta nakshatra). It is this complexity that made Good Friday once occur as late as April 21st (in 2000).
The dates in which the sun enters different rasis in Sayana (western) and Nirayan (Hindu) rasis is given below. Persons born between these dates have their sun position as shown in the table. The sun sign predictions can be followed as per the dates mentioned below– irrespective of year in Gregorian calendar.
Birth Rasi Birth Date
As per Nirayana Sayana
Suns Position System System
Mesham or Aries 15-4 to 15-5 21-3 to 20-4
In contrast, the moon sign varies and can be arrived at only from Astronomical tables or the Panchanga. To determine the moon sign, it is necessray to know an individual's birth date, birth place, and birth time. The birth place is important to know the longitude and latitude (and altitude if it is a high altitude place). The birth time needs to relate with a standard time like GMT - or UK time. If the birth is at night the usual practice is to give the dates adjoining the same – for example, the time can be 01hours, 12 minutes of 7/8 , May 2000 , Singapore ( plus 8 hours to GMT ) or 24:15 San Jose , California USA , Pacific Standard Time ( -Minus 8 hours to GMT ) on 5/6 , May 1984 etc.
The Moon sign is to be calculated by a verified computer program taking into account all the above data. Consulting an experienced astrologer is essential for the same . In addition, the Hindu system gives greater emphasis on the birth star also known as the Nakshatra. While rasi has 30 degrees of arc, Nakshatra has 13.33 degrees of arc and with division of nakshatra to four padas of 3.333 degrees it is more accurate. Finally, in Hindu astrological system the Lagna or ascendant plays a vital role as the focal point of all predictions. Astronomically, the Lagna is defined as the longitude of eastern horizon at the time and place of birth. For accurate predictions the longitudes of the place, Lagna, planets and sensitive points is vital. Detailed information about twenty seven stars or nakshatras will be covered in another article.