SIDERAL AND SOLAR
In Vedic astrology, while the concept of 360 days in a year exists, it's
more relevant to the lunar year and Vedic sacrifices than to modern civil
or astrological calculations. The standard astrological year, however, uses
the solar year of 365 days, and the sidereal year, which is approximately
365.25 days, is considered the most accurate representation of the Earth's
orbit around the sun.
360-day Year:
The Vedic system does mention a year of 360 days, particularly in the
context of Vedic rituals and sacrifices. This is primarily a lunar year,
where each month is based on the lunar cycle. However, this 360-day year is
not used for modern civil or astrological calculations.
365-day Year (Solar Year):
The solar year, which is the time it takes the Earth to orbit the sun once,
is closer to 365 days. This is the year used in the National Calendar of
India, the Saka Calendar.
365.25-day Year (Sidereal Year):
The sidereal year is the most precise measurement of the Earth's orbit,
accounting for the Earth's wobble (precession). It's approximately 365.25
days, leading to the need for leap years in modern calendars to align with
the solar cycle.
Importance in Astrology:
In Vedic astrology, the 365.25-day year is considered more accurate for
astrological calculations, especially when dealing with planetary movements
and the timing of events (Mahadasas).
300-day Year:
The concept of a 300-day year is not directly associated with Vedic
astrology or any standard calendar system.
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The controversy of 360 versus 365 days per year has come into being because
in this day and age those who are studying Vedic astrology are doing so
without being properly educated in Vedic cultural traditions. From a study
of the Vedas and astronomical texts we find that the Sun is the basis for
measuring time. That the year is based on the seasons which is again based
on the movement of the Sun. There are several types of years in vogue in
Vedic culture. The only reference to a 360 day year was used strictly for
sacrificial purposes, the soma-yajna, it was not a lunar or solar year, nor
was it used for civil or astrological purposes. The Vedic Lunar calendar is
actually Solar because it is tied to the seasons which in turn are a Solar
phenomena, thus the Lunar and Solar calendars measure the same length of
time and do not diverge as a function of time as does the 360d/y in
comparison with the 365d/y. Confusion arose after the British introduced
the Gregorian calendar into India, then Lunar tithis became mistakenly
equated with Solar days and the Lunar year of 360 tithis became confused
with a solar year of 360 days. Inspite of this confusion pre-British
classics in Vedic astrology such as Phala Dipika clearly state that the
year for Mahadasa calculation is 365 day year. The claims of those who
state they get better results using a 360 day year is based on ignoring the
holistic approach to astrological analysis and is more or less bluff and
opinion. If we must choose on the basis of opinion then choose the opinion
of the Rishis and previous acaryas who are steeped in the Vedic cultural
traditions of astronomy and calendric science. The previous acaryas follow
the 365 day year for mahadasa calculation. We close this discussion by
quoting part of a letter by the late, learned, Vedic scholar H.R. Shankar
that appeared in The Astrological Magazine:
Some Misgivings On Calculating Mahadasa by H.R. Shankar (AM, January, 1974,
p.93)
"In an article appearing in the October 1973 issue of this esteemed
magazine Hira Gulrajani [who advocated 360 d/y] has raised some serious
doubts on the advisability of timing events guided by Vimsottari
Dasa/Bhuktis in the manner in which is presently in vogue [that is 365
d/y]. He contends that there is an inherent flaw in the method of
calculation and the results thus obtained are an anomaly. According to him
there would be cumulative difference by as much as one month for every 6
years of age of the native between the indicated operative period under
Vimsottari and that of what he terms as actual period. If we are to go with
him in his line of thinking, it would turn out that a native may have to
celebrate his 72 birthday even while he has yet to complete his 71st year
under Vimsottari reckoning. The seed of this confusion lies apparently in
the notion of the contributor is that 'The period of planets given in
astrological works are rated at 30 days a month (360 days for a year of 12
months), etc.' Nothing could be more absurd than projecting, as it does,
the authors of astrological works as so naive and thoroughly lacking in
sense of time measure that they conceived a calendar with 360 days to a
year that is untenable astronomically and ill-suited for religious and even
civil purposes, let alone for timing events. Whereas, actually the same
sages who have codified for us the astrological truths were also giants in
the field of astronomy and have to their credit of evolving systems to
compute with fine accuracy even the age of the Earth.
The basis of all our time measure is the period of our world's rotation on
her axis, defined as our day. Solar days and years are marked by the
consequent apparent motion of the Sun while the Moon's circuit relative to
the Sun marks the lunar month. All calendars extant are mere adoptions of
one of these two systems. Vimsottari being basically a stellar method, it
is logical to conclude that the reference therein is to lunar months and
tithis.
The synodic period of the Moon is the basis for the lunar calendar. Here
the reckoning is done from the day following the New Moon ending with the
next New Moon. The period named as Masa or lunar month is divided into
thirty equal tithis. A tithi is based on elongation taken by the Moon to
cover a segment of 12° of an arc of the zodiac, each multiple of 12 as the
difference in longitude marking the end of a tithi. These are numbered
Shukla (bright) 1 to Shukla 15 during the waxing Moon and Krishna (dark) 1
to Krishna 15 during the waning Moon respectively. The lunar months are
named after corresponding solar months in which the initial New Moon falls.
Twelve lunar months make one Samvastsara, each Samvastsara bearing a
specific name commencing from Prabhava ending with Akshaya completing a
cycle of 60 years. Vimsottari cycle of 120 years corresponds to two
lunar-year cycles.
The duration of a mean tithi being equivalent to 0.98 of a day, there will
be an excess of 10.875 days in a solar year over twelve months. This
difference is periodically reconciled by the introduction of 'Adhika' Masa
in the lunar calendar. When two new-moon-ending lunar months begin within
the same solar month, the second month is termed as Sudha or real and the
first one is Adhika bearing the same name. This, incidentally, results in
the first day of the lunar year always falling between March 14 and April
13/14 of English calendar. In other words, the age reckoned under lunar
calendar would not be different from that of counting from the English
calendar except for a marginal difference of few days, plus or minus.
While the method described in astrological works for calculation of Dasa
and Bhuktis is in units of Tithi, Masa and Samvatsara (as being practiced
by the traditional scholars belonging to old school) the purpose would be
equally served even by the direct application under English calendar.
Astrological predictions being indicative rather than deterministic, a
difference of few days in timing would not substantially distort the
prediction. For those connoisseurs who wish to delve into suksmas division,
the detailed working need necessarily be linked with the phase and movement
of the Moon.
One would, however, be working on very slippery ground in trying to align
operative planetary periods with corresponding events. Invariably, more
than one astrological contributory factor would be involved in bringing
about an event. To identify only one force, to the exclusion of other
planetary factors, with unerring accuracy, as the principle contributor is
more a game of guess than analysis. Being confronted with the ayanamsa
riddle most of the astrologers resort to this method of stretching and
pruning the operative period to accommodate past events and then take off
from that point. Though this method is widely used, individual experience
and talents alone are the decisive factor when it actually clicks. . . . "
While we do offer services on this site it is primarily educational. Any
money that we make from our services go toward continued study and
publishing of well-researched articles that set a high standard in the
jyotish community. As a brahmana my primary vocation is to study and share
my knowledge with others. In traditional Vedic culture the general public
and especially those who benefit directly from that knowledge help to
support the teacher so that he can spend more time in deep study and
continue the cycle. If your knowledge has been expanded and you are
inspired by the Lord in your heart please donate an amount that you are
comfortable giving.
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The difference between sidereal and solar days arises
because the Earth
is simultaneously rotating on its axis and orbiting the Sun. A sidereal
day is the time it takes for the Earth to complete one full rotation
relative to the *distant stars,* roughly 23 hours, 56 minutes, and 4 seconds.
A solar day, on the other hand, is the time it takes for the Earth to
rotate until the *Sun *appears in the same position in the sky,
approximately 24 hours. The Earth's orbital motion around the Sun requires
it to rotate slightly more than 360 degrees to bring the Sun back to the
same position, which is why a solar day is longer than a sidereal day.
The planets of our solar system both orbit around Sun and rotate on their
axis. These two rotations allow for multiple definitions of what a day is.
The sidereal day is the day according to the stars. It is the time it takes
for a point on a planet facing a particular star to then face it again. On
Earth, this time is 23 hours and 56 minutes. The unit of time called a
solar day is the time it takes for a point on a planet facing Sun to then
face Sun again. On Earth, this time is 24 hours. The difference between the
sidereal and solar day is due to the orbital motion of the planet. For the
planets with their orbital motion in the same direction as their rotation
(Mercury, Earth, Mars, Jupiter, Saturn, and Neptune), the solar day is
longer than the sidereal day. For Venus, the only planet with retrograde
rotation, the sidereal day is longer than the solar day.
https://youtu.be/WWw4JY2dNXM demo in you tube
A solar day can be defined as the time it takes a planet to rotate once
relative to the Sun, while a sidereal day is the time it takes a planet to
rotate once on its own axis. A solar day is what we Earthlings usually
mean by the word “day.” It’s the 12 a.m. on Monday to 12 a.m. on Tuesday
kind of day. A sidereal day (pronounced si-der-e-al) is more like a
planet’s true rotation period, relative to the rest of the universe. Why
are these things different? Because planets orbit the Sun. Because as
they orbit, they change position relative to the Sun.
In Earth’s case, it takes about 23 hours and 56 minutes to rotate once on
its own axis, but because Earth moves through space during that time
(changing positions relative to the Sun), it takes an extra 4 minutes to
rotate once in reference to the Sun. And according to my math, 23 hours and
56 minutes, plus an extra 4 minutes, makes Earth’s solar day 24 hours long.
The situation is similar for Mars. A Martian sidereal day is about 24
hours and 37 minutes, while a Martian solar day is more like 24 hours and
40 minutes. For both Earth and Mars, the difference is small. Most of the
time, it’s not worth mentioning. But on Mercury, a sidereal day is 59
Earth days long, while a solar day ends up being 176 Earth days in length. You
see, Mercury rotates very, very slowly. Over the course of one sidereal
day, Mercury travels two-thirds of the way around the Sun. That puts
Mercury in a very different position, relative to the Sun, at the end of a
sidereal day. As a result, Mercury’s solar day ends up being longer—a
whole lot longer—than Mercury’s sidereal day.
The precession of the Earth's rotation axis introduces another difference
between sidereal time and solar time. This is seen in how the year is
measured. A year is defined as the orbital period of the Earth. However, if
you use the Sun's position as a guide, you come up with a time interval
about 20 minutes shorter than if you use the stars as a guide. The time
required for the constellations to complete one 360° cycle around the sky
and to return to their original point on our sky is called a sidereal
year. This
is the time it takes the Earth to complete exactly one orbit around the Sun
and equals 365.2564 solar days. The slow shift of the star coordinates from
precession means that the Sun will not be at exactly the same position with
respect to the celestial equator after one sidereal year. The tropical year
is the time interval between two sucessive vernal equinoxes. It equals
365.2422 solar days and is the year our calendars are based on. After
several thousand years the 20 minute difference between sidereal and
tropical years would have made our summers occur several months earlier if
we used a calendar based on the sidereal year.
n is the king of all planets. All planets revolve around it. Astrology
considers Sun a planet, but in terms of geography, it is a star. Revolution
of Earth around the Sun changes day, night and Ayan (Uttarayan and
Dakshinayan).
The secret of the sidereal time is hidden in the process of
circumambulation of Sun by Earth. Earth rotates on its axis for 24 hours.
Earth rotates 360 degrees on its axis in 24 hours revolving around the Sun.
This completes one whole day called the solar day. Ideally, it is said that
24 hours is the rotation time, though this duration is 23 hours, 56 minutes
and 4.09 seconds. The remaining 3 minutes 56 seconds are considered as the
sidereal day, which is the remaining part of the solar day. In short, a
sidereal day can be defined as the time taken to rotate from a one-time gap
to another time gap from the middle point. The remaining time between this
is called the sidereal time.
Importance of Sidereal Time in Astrology
The earth is rotating on its axis once a day, but for an observer, the
celestial sphere is rotating. Thus sidereal time is local time reckoned
according to the apparent rotation of the celestial sphere. In other words,
whenever the time is reckoned with reference to the sidereal day, it is
called sidereal time. The sidereal time is zero when the first point of
Aries in Sayana or vernal equinox crosses the observer's meridian. Sidereal
time can, therefore, be defined geometrically as an hour angle of the
vernal equinox.
One Sidereal day has 24 sidereal hours. According to the method of
calculation of time, this is considered the sidereal time. Sidereal time is
very important in astrology. This is because the situation of the zodiac
during this period in any country or place every day will be the same in
the next cycle. That means the position of signs in one sidereal time will
be the same in the next 24 hours. The position of the Ascendant, tenth and
the fourth house will also be the same. This is the reason why astrologers
need accurate sidereal time while they prepare birth-chart. It is only
through this that they will get the right results.
Ascendant or Lagna is that sign, Rashi or the point of the ecliptic
which is rising in the eastern horizon corresponding to the first house of
horoscope. It, therefore, has the greatest importance without which we
can’t proceed with the casting of a horoscope.
In calculating the birth chart, the first step is to calculate
the sidereal time and then to go for the ascendant. It is not enough to
know the rising sign, rather one must know the exact degrees of the sign.
The Sidereal Day is Longer Than the Solar Day: Why?
The sidereal day is longer than the Solar day because Earth completes one
cycle in one sidereal day. However, during this period, Sun rotates in the
zodiac 10 times. So, Earth has to rotate more to reach the position of
Sun. Earth
takes 4 minutes more for this. That means the Sun rotates for 360.9860.
Xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx K Rajaram IRS
1525
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