Astronomy as Relevant to Astrology

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The Basic Concepts

Rajeev Jhanji

The Branches of Vedic Astrology

Jyotish is considered to be one of the Vedangas

(part of Vedas) propounded by lord Brahma by the scientific study of

which human beings can accomplish virtue. Jyotish shastra or the

science of Vedic astrology, is a compilation of 4,00,000 verses (vide Narada Purana, II.50.2). Vedic astrology has mainly three branches – Siddhanta (the principle), Jataka or Hora (astrology for individuals) and Samhita (astrology for masses).

• Siddhanta, also known as Ganita, deals

with the mathematical calculations, the methodology of calculating

planetary positions, knowledge about time, place, direction, lunar and

solar eclipses, their rising and setting, planetary movements,

conjunctions, retrogression, etc.

• Jataka

(Hora) deals with the techniques of interpretation of horoscopes of

individuals. It describes signs, planets, their qualities, family

situations/ circumstances at the time of birth, arishta (mishaps),

longevity of the native, different dasha systems and their results,

profession (sources of livelihood), ashtakavarga, varied types of

yogas, results of planetary positions in different houses, signs,

nakshatras, aspects of planets, planetary combinations, female

horoscopy, circumstances at the time of death, cases of unknown birth

time, etc. The term `Hora' has been applied to `Jataka' or natal

astrology, as well as to the `Muhurta' or electional astrology (i.e.,

selecting the appropriate moment to commence an undertaking).

• Samhita

is that branch of astrology which is related to masses and is a

compilation of varied subjects like the results of rising and setting

of planets, appearance of different types of comets, varied types of

chakras, predicting about rainfalls, earthquakes, natural disasters and

epidemics, results of planetary movements on kingdoms, nations, masses

and commodities, etc.

The Geocentric System

It

is a human tendency to refer to other things in relation to oneself.

Sitting in a moving train, we see things passing by the train – trees,

farms, hutments, etc. A common question arises in our mind – which is

the station coming next? At the back of our mind we do know that it is

not the station which is going to come, it is the train which will

reach the next station. Similarly we refer to the rising and setting of

the Sun. But we do know that it is not the Sun which is rising or

setting, it is the spin of the earth which makes it appear so.

Because

we feel stationary on the solid earth, the sky seems to spin around us

in complicated ways. In our quest to understand what we see, our

ancients had evolved a most innovative and powerful tool.

As

nothing is stationary in the universe, whether it is a satellite or a

planet or even a star, it is convenient to imagine our position in the

universe – the earth – as its centre and the whole of the universe

moving around us in constant motion. Thus considering the relative

positions and movements of all heavenly bodies with respect to the

earth is the Geo-centric system. On the other hand, when we consider

the relative position of planets (including the earth) in respect of

the Sun, it forms the basis of the Helio-centric system. Vedic

astronomy and astrology are essentially geo-centric in their concept.

The Earth

The

earth is spherical and rotates from west to east around its axis. The

axis of the earth is an imaginary line which, passing through its

centre, connects its two poles, the north pole and the south pole.

Another imaginary line running across the largest circumference of the

earth, equidistant from its poles and running in an east-west

direction, is called the equator.

The Celestial Sphere

Think

of the sky as a great, hollow, crystalline sphere surrounding the

earth. Imagine the stars to be attached to the inside of the sphere

like thumbnails stuck in the ceiling. The sphere takes one day to

rotate, carrying the Sun, the Moon, the planets and the stars from east

to west. We know that the sky is not a great, hollow, crystalline

sphere. The stars are scattered through space at different distances,

and it isn't the sky that rotates once a day. It is rather the earth

that rotates once in a day around its axis. It is convenient as a model

of the sky. This model of the sky, the Celestial sphere, is an

imaginary hollow sphere of very large radius (infinity) surrounding the

earth and to which the stars seem to be attached. On this imaginary

sphere the celestial equator, the celestial poles, and other reference

points are marked as they are done on the earth; these represent the

extensions of the equator and the poles, etc., of the earth into

infinity.

 

Zodiac

The

earth takes one year to complete its rotation around the Sun. From the

earth, it appears that the Sun moves around the earth. This apparent

path of the Sun is known as ecliptic. An imaginary belt of 18 degrees

width with ecliptic in its centre is known as the zodiac. Many groups

of stars appear to have been studded on this imaginary belt. Vedic

astrology recognizes 27 such groups of stars called nakshatras.

The

zodiac encircles the earth like a circle consisting of 360 degrees. If

this circle is divided into 27 equal parts, each part will be of 13

degrees and 20 minutes arc, known as a nakshatra. Each nakshatra is

further divided into 4 quarters (padas or charanas), of 3 degrees and

20 minutes arc each.

Twelve divisions of the zodiac will have an arc of 30 degrees each, known as rashis (or signs).

 

The

above figure shows rising of the Sun in the eastern horizon. The line

passing through the centre of the Sun is the ecliptic, the apparent

path of the Sun created by its `revolution' around the earth during its

annual journey. The group of stars, referred to as the nakshatras, are

the fixed reference points in the zodiac used to locate the position of

the Sun, the Moon and other heavenly bodies. All the planets considered

in Vedic astrology for the purpose of interpretation, do not decline

beyond the belt of the zodiac. They may be on the ecliptic or towards

the north or sourth of the ecliptic depending on their latitude with

reference to the ecliptic.

 

For example, the orbit of the Moon is inclined at an angle of 5 degrees

to the ecliptic. The Moon does not go beyond 5 degrees on either side

of the ecliptic. The orbit of the Moon cuts the ecliptic at two point.

In its orbit, when the Moon is on the ecliptic while moving from south

of ecliptic to north, this point is known as Rahu or the ascending node

of the Moon and when the Moon is on the ecliptic while moving from

north of ecliptic to south of ecliptic, this point of intersection is

known as Ketu or the descending node of the Moon.

 

The point of sunrise with respect to the observer keeps changing during

the year. If A is the point of sunrise when the Sun is at vernal

equinox (around March 21 every year), the point of sunrise will appear

to move northwards till it reaches the summer solstice (B) on or around

June 21. from this point it will start its southernly journey

(Dakshinayana) during which it reaches the autumnal equinox (again A)

around September 23 and further until it reaches winter solstice ©

around December 22. At this stage it starts its northward journey

(Uttarayana).

Tropical Zodiac

The

most crucial point in the division of a circle is to know the starting

point of the circle. The point where the ecliptic cuts the celestial

equator is known as equinox. There are two such equinoxes – the vernal

equinox and the autumnal equinox. When the Sun is passing from the

southern hemisphere to the northern hemisphere, it cuts the equator at

vernal equinox. When the division of the circle of the zodiac is with

reference to vernal equinox as its starting point, the zodiac is

referred to as the Sayana (or tropical) zodiac, the divisions

of this zodiac into twelve equal parts are the Sayana rashis, and the

positions of planets in this zodiac represent the Sayana longitudes of

the planets.

The Precession of Equinoxes

If

we could watch the sky for a few hundred years, we would discover that

the north celestial pole is moving slowly with respect to Dhruva

(Polaris) star. The celestial poles and the celestial equator, supposed

to be the fixed reference marks, are moving very slowly because of the

slow change in the direction of Earth's axis of rotation. This slow

top-like motion is called precession. Earth's axis sweeps around in a

cone, taking almost 26,000 years for each sweep.

Precession

is caused by the gravitational pull of the Sun and the Moon. Because

earth is not a perfect sphere – it has a slight bulge around its

equator – Sun and Moon pull on it, trying to make it spin upright in

its orbit. This forces earth's axis to precess.

The

result of this precession is that vernal equinox, the cutting point of

the ecliptic and the celestial equator, drifts westward on the ecliptic

by an approximate angle of 51 seconds of an arc each year. So we have a

new vernal equinox every year and hence a new staring point of the

Sayana zodiac. This results in the shifting of the Sayana signs.

 

Sidereal Zodiac

The

Vedic system does not depend on this shifting zodiac and relies on a

fixed point on the zodiac as its starting point. There is no clear cut

demarcation of this starting point in the zodiac. Some consider this

point to be 180 degrees opposite to the Chitra nakshatra. Some consider

it to be slightly to the east of the Revati nakshatra, while still

others opine differently.

When the division

of the circle of the zodiac is with reference to the Vedic starting

point, the zodiac is referred to as the Nirayana (or Sidereal) zodiac,

the twelve equal parts are the Nirayana rashis, and the positions of

planets in this zodiac represent the Nirayana longitudes of the planets.

 

The

angular difference between the vernal equinox and the Vedic starting

point of the zodiac is known as the Ayanamsha. When the Vedic starting

point is with reference to Chitra nakshatra, the Ayanamsha is refered

to as the Chitrapaksha Ayanamsha. According to this system the first

point of Sayana zodiac and Nirayana zodiac coincided in the year 285

A.D. The corresponding value of this Ayanamsha on January 1997 is

23°48'56".

 

 

 

 

 

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