About Astrology

Prof. Dr Prajarao  2019-04-20 09:51:04

About Astrology

I. Introduction

Astrology or some modification of its version like numerology, palmistry or Tarot card reading was existing in one form or other in almost all civilizations. Whether one calls it a science or blind belief it played a vital role and continues to play a critical role even in the present times of Internet. Basically astrology attempts to find position and properties of different planets and their interaction with human behavior. It has a lot of scientific basis – to give an example it is a known fact that moon is responsible for the high and low tides of the sea – that sun flares are responsible for electromagnetic radiation – which in turn affect communications. The word planetary positions mean the astrological properties like moons phases of brightness and many other astrological properties like 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 / newspapers as they are given in terms like – predictions based on position of sun at birth, position of moon at birth, birth star etc. Another problem faced by many believers depends on the necessary calculations for persons born or residing at a place outside India. In this introductory articles the different astrological data based on the birth particulars and their astronomical basis are explained – so as to enable a person how to use general predictions based on the limited birth data available – with all its variations and the limitations of the predictions.


II. Astrology and its parts

Astrology consists of three parts – namely (a)Sidhdhanta or theoretical astronomical calculations for finding the planetary properties, (b) Predictive astrology – 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 parts there are alternative techniques and methods – based on data available and once own faith.

For example in the pre computer era the theoretical calculations of planetary properties were done using old slokas based on classics like “Surya Siddhanta” – in which the affect of place of birth is not fully taken. Also the theory itself was requiring modifications due to astronomical events in the past which might have made changes in the planetary positions and their properties. But with availability of computers and their use for rocket and satellite launching the astronomical calculations of planetary positions at different places of earth have got fresh tools available for accurate and error free astronomical calculations. 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 possible errors in calculations and very accurate calculations for any place of birth in the world has become possible by using modern astronomical equations and used in satellite launching. In fact the same equations used in satellite launching are incorporated by the author and many for astrological calculations. Thus modern tools have become handy to apply to an ancient branch of knowledge.

III.Basic Astronomy

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 – to avoid the confusion that arises out of so many systems and terms generally used.

The planets (like Mercury, Venus, Mars, Jupiter, and Saturn) move around sun with varying speeds and orbits. In turn the planets have their own satellites – like earth having moon as its satellite. Each of these celestial object rotate around itself like a toy – which we can call as spin in addition to the rotation around their parent object. 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 - causing 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 moon takes about 28 days to complete one rotation around earth.

To give a nomenclature to different positions of the sky or Zodiac some frame of reference is to be used. Thus the Zodiac or sky is divided into 360 degrees – each portion identified by so called star or stellar position. But the stars themselves or their parent group called “Galaxy” is moving with considerable speed.

  • Thus to summaries the movements
  • Moon is spinning around itself and rotating around earth
  • Earth is spinning around itself and rotating around sun
  • Sun is moving in the sky with great speed – sun is a star
  • Many stars or suns make a galaxy and galaxy is moving with great speed

These complex motions make calculation of the position of any celestial body a meaningless or unreliable proposition. But as proposed in modern science like Theory of Relativity – ancient sages of Hindu astrology were aware of this knowledge – That motion is absolutely relative – and without defining the positions properties of the observed and observer the data gathered has no meaning. In the present context to fix a planets position – there is no absolute “Frame of Reference” as the stars, stellar system and galactical system itself is moving. It is like 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 say with stellar system as reference – the stellar system itself as 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 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 a fixed one – equal to the one existing at the time of original creation defined in the Hindu mythology. Thus the stellar system or zodiac starts with the star Aswani – and is fixed irrespective of time of birth.

In contrast the Sayana system calculates based on so called present position of the stellar system – as the stellar movement in a few days time is very small compared to the planetary movements in that period – because of the great distances of stars and galaxies.

In addition to this complexities of motion, we have an additional problem of “Inclined plane of rotation of earth around the sun”. This inclination of about 23.5 degrees has a steady but great effect on the calculations. In-fact it is this inclination that gives rise to different seasons of summer winter etc. in the year. For the astronomical calculations this has a telling effect. To understand its effect – the North – South axis of earth is now pointing to Polar star (or Dhruva Nakshatra of Hindu astronomy). But this axis moves with a steady but telling effect of about 55 seconds of angular arc – thus the present axis point of 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 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.

IV. Zodiac versus Solar and Lunar Cycles

Irrespective of 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 cave man to modern man, the cycle or calendar in the year has great effect on our daily life as seasons are controlled by the movement of sun and moon versus the inclination of about 23.5 degrees. The difference between 360 degrees movement of earth’s rotation around sun in about 365.24 days gives rise to the Solar year – this difference of about 5.24.. days are adjusted in different calendars by different methods. In the popularly used Gregorian calendar - this is adjusted by the so-called leap year. It is worth while to note that the definition of leap year itself has undergone great changes – 10 days were dropped in 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 calendar system is a different and big subject by itself.

Again it is the ingenuity of Hindu Sages that gave a permanent and everlasting and self rectifying calendar. In the nirayana system they followed, the zodiac is defined into the following 12 rasis each consisting of 30 degrees of arc. 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.

  1. Mesham or Aries
  2. Vrushabham or Taurus
  3. Mithunam or Gemini
  4. Karkatakam or Cancer
  5. Simham or Leo
  6. Kanya or Virgo
  7. Tula or Libra
  8. Vruschikam or Scorpio
  9. Dhanus or Sagitarius
  10. Makaram or Capricorn
  11. Kumbham or Aquaris
  12. Meenam or Pisces
  13. Method of using rasis in different calendars

The movement of sun to different rasis is 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 Nirayana and sayana system.This movement of sun to different rasis is called solar ingress or Sankramanam – it is this which causes the seasons and different festivals. For eg in christian calendar while Christamas is on a fixed date of December 25th, the Good Friday is related with 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 the Good Friday to occur as late as April 21st in 2000 – almost repeating this late coming in 60 years.

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

  1. Vrushabham or Taurus 16-5 to 15-6 21-4 to 20-5
  2. Mithunam or Gemini 16-6 to 15-7 21-5 to 20-6
  3. Karkatakam or Cancer 16-7 to 15-8 21-6 to 20-7
  4. Simham or Leo 16-8 to 15-9 21-7 to 20-8
  5. Kanya or Virgo 16-9 to 15-10 21-8 to 20-9
  6. Tula or Libra 16-10 to 15-11 21-9 to 20-10
  7. Vruschikam or Scorpio 16-11 to 15-12 21-10 to 20-11
  8. Dhanus or Sagitarius 16-12 to 14-1 21-11 to 20-12
  9. Makaram or Capricorunus 14-1 to 14-2 21-12 to 20-1
  10. Kumbham or Aquaris 15-2 to 14-3 21-1 to 20-2
  11. Meenam or Pisces 15-3 to 14-4 21-2 to 20-3

In contrast the moon sign varies and can be arrived at only from astronomical tables or panchanga. For knowing moon sign the data required is birth date, birth time and birth place. The birth place is important to know the longitude, latitude (and altitude if it is a high altitude place). The birth time is to taken and then 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 eg the data can be 01hours, 12 minutes of 7/8 , May 2000 , Singapore ( plus 8 hours to GMT ) or 24:15 Sanjose , 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 good computer program taking into account all the above data. Consulting a good astrologer is essential for the same . In addition the Hindu system gives greater emphasis on birth star or 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 lagna is nothing but 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.