SJVS LESSON ONE

SJVC Lesson 1
Astronomical Definitions in Jyotish
Compiled by Gauranga Das, °c SJVC & Gauranga Das
JAYA JAGANNATHA!
Bgvn^ prm\ p \ y g \  v dA½mm^ .
E/-k D\ >yOEtq\ horA gEZt\ \ sEht Et c ;
(BPHS. 1.2.)
bhagavan paramaü puõyaü guhyaü vedàïgamuttam .
triskandhaü jyautiùaü horà gaõitaü saühiteti ca ..
"O Supreme sage! Astrology, the supreme limb of the Vedas, consists of three
divisions. Viz. Hora, Ganita
and Samhita."
This is one of the beginning shlokas of Brihat Parasara Hora Sastra, which
describes that Jyotish has
three skandhas or divisions, namely Hora (natal astrology), Ganita (astronomical
calculations) and Samhita
(omens and other signs). Varaha Mihira especially mentions, that an astrologer
should be well versed in all
of these three divisions. According to Prasna Marga, there's two subdivisions of
Ganita, or astronomical
calculations, namely Gola (spherical astronomy) and Ganita (general
calculations), out of which the latter
deals with general description of the heavenly bodies, while the former deals
with the factors which are due
to the shperical nature of the Earth and other Grahas.
The heavenly bodies
f Z Evþ þv#yAEm Bg}hAZA\ pErE-TEtm^ .
aAkAf yAEn d [y t >yoEtEb
MbA yn kf, ;
t q n"/s\+AEn g}hs\+AEn kAEnEct^ .
tAEn n"/nAmAEn E-Tr-TAnAEn yAEn v{ ;
(BPHS. 3.2-3)
÷çõu vipra pravakùyàmi bhagrahàõàü paristhitim .
àkà÷e yàni dç÷yante jyotirbimbànyaneka÷aþ ..
teùu nakùatrasaüj¤àni grahasaüj¤àni kànicit .
tàni nakùatranàmàni sthirasthànàni yàni vai ..
"O brahmin, listen to me, I shall give an account of the placement of the
heavenly bodies. Out of the many
luminous bodies that are seen in the heavens, some are called stars (nakshatras)
and the others are named
as planets (grahas). Those which have no movements and are fixed in their
places are called nakshatras, and
the moving bodies are the grahas."
According to the above verse there are two classes of heavenly bodies: the
non-moving ones, or the stars
(nakshatras) and the moving ones, or the planets (grahas). To measure the
movements of the grahas in the
background of the stars, we should determine points of measurement on the sky.
1 The structure of the earth
According to the Surya Siddhanta (ancient astronomical treatise) the Earth
(Bhumi) could be considered a
globe, which rotates around its own axis. The two ends of this axis poke through
the surface of the Earth
at the north and south pole.
1SJVC Lesson 1 Astronomical Definitions in Jyotish
1.1 The Earth's Equator (Vishvarekha)
This is an imaginary line running around the earth in the exact middle between
the south and north poles.
This divides thre Earth into a northern and southern hemisphere. The
difference between the two is especially
visible in the changes of the seasons (determined by the yearly motion of the
Sun). In June for example we
have summer in the northern hemisphere but simultaneously winter in the southern
hemisphere. Therefore
the location of the nativity (place of birth) will be a determinant factor in
the astronomical calculations that
we carry out. Therefore it is necessary to be able to determine the location by
certain measurements. To
ascertain a point on the earth globe, we will need two coordinates: the latitude
and the longitude of the
place.
1.2 The Latitude (Akshamsa)
This is the angular distance of the place from the Equator towards the North or
South. It is measured in
degrees, minutes and seconds of arc. The equator is the 0
±
point, and the poles are at 90
±
to the south and
the north. The southern or northern latitude of the nativity will determine the
time of sunrise and sunset
and the duration of the day and night, which have important role in a number of
calculations in Jyotish.
1.3 The Longitude (Rekhamsa)
The longitude is the vertical measurement of degrees. The earth can be divided
into 360 longitudinal meridians, each of the extent of 1
±
Now the choice of the beginning point, or 0 .
±
is not determined astronomically. In
the ancienc India the 0
±meridian was the one intersecting the ancient town of Ujjain, where one of the
Jyotirlingas (Lord Shiva's manifestation in a glowing stone) is situated. This
Jyotirlinga is called Mahakaleshvara,
and as the astrology is the science of the measurement of the quantity and
quality of time (Kala), this
was naturally taken as 0
±
In the modern times the latitude is better known as the angular distance from .
Greenwich, where the officially accepted 0
±meridian runs. Thus a place may have either eastern or western
longitude from Greenwich and either southern or northern latitude from the
Equator. For example New York
lies at 74
±West of Greenwich and at 40
±
43' north of the equator. This is usually indicated thus: 74W00,
40N43. Paris is located at 2E20 and 48N52. The longitude will influence
which planets will be above the
horizon, and which ones will be under the horizon. For example while there's
noon in New York, there will
be night in Delhi. So in one chart the Sun is above the horizon, while in
another it's under it, although the
natives were born at the same time cosmically. So the latitude determines, where
the Lagna (ascendant)
will be, i.e. which sign or nakshatra will be rising on the eastern horizon at
the time of birth.
2 The division of the sky globe
We can look at the sky above us as a globe around the Earth. Thus for
determining positions in the sky we
will again need two coordinates.
2.1 The Celestial Equator (Nadivritta)
The celestial equator is the extension of the Earth's equator in the skies, and
it divides the sky globe into
two halves.
2SJVC Lesson 1 Astronomical Definitions in Jyotish
2.2 The Declination (Kranti)
This will be the angular distance of a heavenly body from the celestial equator.
It will be either negative if
the planet is above the northern hemisphere, or positive, in case the planet is
above the eastern hemisphere.
The declination is also called Ayana. Thus the Sun's yearly movement is divided
into two parts, called
Uttarayana and Dakshinayana. The Sun reaches the southest point of its traectory
at the time of the winter
solstice (Dec. 23) and from there it begins travelling north, thus its
declination gradually decreases. It
crosses the equator at the time of the vernal equinoxe (March 21) when on the
whole Earth the duration
of day and night is equal. Then it proceeds towards the northern hemisphere up
until the point of summer
solstice when the Sun is above the northest point of the Earth and we have the
longest day in the northern
hemisphere and the shortest night. After that the declination begins increasing
from the lowest negative
degree, and coming to the point of autumn equinoxe. At this time the declination
of the Sun equals 0 again,
and it keeps increasing positively till the point of winter solstice again.
2.3 The Ecliptic (Ravimarga)
The ecliptic is the Sun's above described path, which forms a curved line, which
once a year touches the
Tropic of Cancer (during summer solstice) and also once the Tropic of Carpicorn
(during winter solstice),
and crosses the equator twice a year at the time of the equinoxes.
2.4 The Celestial Latitude (Kshepa)
This is the angular distance of a planet from the ecliptic (the Sun's path). It
is negative if the planet is to
the north from the ecliptic and is positive if it is to the south from it.
3 The Circle of the Zodiac
3.1 The Zodiac (Bhacakra)
This is a broad band in the sky extending 9 degrees on either side of the
ecliptic and comprised of different
constellations (nakshatras). The planets never get very far away from the
ecliptic, therefore they are always
within this belt. As the circle has no beginning, again, as in the case of the
terrestrial longitudes, we
should select an arbitrary point in the skies as the beginning of the zodiac,
which will be determined by the
placement of certain stars (nakshatras), since Parashara gave the
definition that only the grahas move, and
the rest of the bodies is fixed. The zodiac consists of 360 degrees of arc
(rekhas). Each degree has 60 minutes
(kala) and each minute has 60 seconds (vikala). Thus the full extent of the
zodiac may also be expressed
as 21 600 minutes or 129 600 seconds of arc. There are further submeasurements
like para, paratpara and
tatpara.
3.2 The 0
±
of the Zodiac
This point is determined on the basis of the placement of the star which is
known as Zeta Piscium in the
west. This star is no longer visible so much, therefore we can determine the
exact middle of the zodiac (180
±
(
by the position of the star Spica.
3SJVC Lesson 1 Astronomical Definitions in Jyotish
3.3 The Tropical (Sayana) and Sidereal (Nirayana) Zodiac
The above statements reveal that the zodiac used in Vedic astrology is linked
with the stars, and is immovable
in comparison to them. On the other hand, observation confirms that the
Sun's yearly cycle on the Ecliptic
does not fully coincide with it's making a complete circle relative to the
stars, but the former is a bit shorter.
This in other words means that the Sun at the time of vernal equinoxe will not
come back to the same point
of the sidereal zodiac, but a little less than that. This is called precession.
The tropical zodiac is fixed to
the Sun's movement through the ecliptic, and thus it's called the movable
(sayana) zodiac.
3.4 The Precession (Ayanamsha)
As the two zodiacs are rotating compared to each other, there's a certain cycle
to it, which is 25 870 solar
years long. Then there is a certain point of coincidence, when the 0 degrees of
both zodiacs exactly coincide.
Although authorities differ on this, the most widely accepted opinion is
that the last coincidence was at
the vernal equinoxe in 285 AD. There are also different opinions regarding
the yearly value of precession.
Varaha Mihira states that it's approximately 50 1/3 vikalas or seconds of arc.
Of course the precession has
a negative value, so the vernal equinoxe is pushed back to Pisces, then Aquarius
etc. over the years. Also
the value of the ayanamsha is not linear but cyclical, as it describes the
change of the position of the ecliptic
towards the celestial equator.
3.5 The Ayanamsha Value
Out of the number of suggested precessional values, the Lahiri or Chitra Paksha
Ayanamsha stands out as
the most accurate, although testing with divisional charts indicates that even
this may be inaccurate for
a couple of seconds of arc. But until a more exact ayanamsha value is suggested,
this is recommended for
calculations. Lahiri Ayanamsha is verified on the basis of the placement
of the above mentioned star Spica,
which forms the exact middle of the Chitra nakshatra. According to this system,
the Ayanamsha value at
the present time is 23
±
52'40". This means that the Sun will this much fall behind the 0
±Aries of the sidereal
zodiac at the time of the vernal equinoxe. So it will be somewhere around 6
degrees of Pisces.
4 The Divisions Of The Zodiac
4.1 The Nakshatra Chakra
As we have mentioned earlier, the basis of the division of the zodiac is the
placement of different constellations
in it. The constellations are divided into areas in the sky, each of which
covers 13
±
20' of the whole zodiac.
Thus there are 27 nakshatras beginning from Ashwini and ending with Revati.
There is also a 28th nakshatra
called Abhijit. This is an intercalary Nakshatra, i.e. it does not have any own
extension, rather it ocuppies
the last quarter of the Uttarashadha Nakshatra and the first 1/15th part
of the Shravana Nakshatra, i.e. it
extends from 276
±
40' to 280
±
53 1/3' of the zodiac. The division of Nakshatras is based on the Moon, which
makes a complete cycle in the zodiac within one month. The Moon spends
approximately one day in each
Nakshatra. Every Nakshatra may be further divided into four quarters (padas) 3
±
20' each. Thus the zodiac
will have 108 nakshatra padas, which are also called navamshas (1/9th of a
sign).
4SJVC Lesson 1 Astronomical Definitions in Jyotish
4.2 The Rasi Chakra
There other main method for the division of the zodiac is based on the Sun. The
Sun travels through the
zodiac within one year, and during this he meets the Moon 12 times. Thus there
will be 12 months within
one year. Therefore we could divide the zodiac into 12 rasis or signs, in which
the Sun will spend one month
each. These signs will have an extent of 30
±
.
4.3 The Divisional charts (Amsas or Vargas)
The signs of the zodiac may be further divided into subparts. Maharishi
Parashara and other Jyotish authors
have specifically mentioned the following subdivisions of the signs: Hora
(D-2), Drekkana (D-3), Caturthamsa
(D-4), Panchamsa (D-5), Sashthamsa (D-6), Saptamsa (D-7), Ashtamsa (D-8),
Navamsa (D-9), Dasamsa
(D-10), Rudramsa (D-11), Dwadasamsa (D-12), Shodasamsa (D-16) Vimsamsa (D-20),
Siddhamsa (D-24),
Nakshatramsa (D-27), Trimsamsa (D-30), Khavedamsa (D-40), Akshavedamsa (D-45),
Shashtyamsa (D-60),
Ashtottaramsa (D-108), Dwadasamsa-Dwadasamsa (D-144) and Nadiamsa (D-150). The
most important
divisional chart is however the Navamsha, as it is based both on the division of
the Sun and the Moon.=20
4.4 The Celestial Longitude (Sphuta)
The position of the planets in the zodiac is expressed through the celestial
longitude, which is counted from
the beginning of Aries. Sometimes the degree of the planet within a sign is
indicated, or also its position in
the Nakshatra padas and the divisional charts.
Assignments
1. Explain the changing of the seasons and its connection with the above
mentioned astronomical factors.
2. There are some days of the year when the Sun either doesn't rise or set above
certain parts of the world. Why is that. Please explain....