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== परिचयः || Introduction ==

== परिचयः || Introduction ==

Astronomy is the main subject of the text Vedanga Jyotisha. Even during Rigvedic times astral sciences were highly developed where people acquired knowledge of the movement of sun and moon for knowing the seasons which was important in performing yajnas such as Darsapurnamasa and Chaturmasya. Ancient people had knowledge of the calculations for eclipses, full moon (Amavasya) and new moon (Purnima) days, of nakshatras (stellar constellations) as it is required for determining the commencement of specific Yajnas.<ref name=":1" />  

Astronomy is the main subject of the text Vedanga Jyotisha. Even during Rigvedic times astral sciences were highly developed where people acquired knowledge of the movement of sun and moon for knowing the seasons which was important in performing yajnas such as Darsapurnamasa and Chaturmasya. Ancient people had knowledge of the calculations for eclipses, full moon (Amavasya) and new moon (Purnima) days, of nakshatras (stellar constellations) as it is required for determining the commencement of specific Yajnas.<ref name=":1" />  

== Jyotisha in Vedas ==

== Jyotisha in Vedas ==

Like many branches of knowledge, the beginnings of astronomy in Bharatavarsha have been traced back to the Vedas. Vedanga Jyotisha text is found in two recensions - Rigveda Jyotisha and Yajurveda Jyotisha. Though the contents of both the recensions are the same they differ in the number of verses contained in them. Rigveda version contains only 36 verses whereas the Yajurveda version contains 44 verses, the difference attributed to the addition of explanatory verses given by the adhvaryu who used them.<blockquote>यथा शिखा मयूराणां नागानां मणयो यथा । तद्वद्वेदाङ्गशास्राणां ज्योतिषं (गणितं) मूर्धनि स्थितम् ॥ १९ ॥ (Veda. Jyot. 4) </blockquote>Like the crests on the heads of peacocks, like the gems on the hoods of the snakes (cobras) astronomy (mathematics) is at the highest position of vedanga shastras (the six ancillary branches of knowledge).

Like many branches of knowledge, the beginnings of astronomy in Bharatavarsha have been traced back to the Vedas. Vedanga Jyotisha text is found in two recensions - Rigveda Jyotisha (called Archa-jyotisha) and Yajurveda Jyotisha (called Yajusha-jyotisha).<ref name=":15">Kolachana, Aditya & Mahesh, Kaluva & Ramasubramanian, K.. (2019). Main characteristics and achievements of ancient Indian astronomy in historical perspective. 10.1007/978-981-13-7326-8_24.</ref> Though the contents of both the recensions are the same they differ in the number of verses contained in them. Rigveda version contains only 36 verses whereas the Yajurveda version contains 44 verses, the difference attributed to the addition of explanatory verses given by the adhvaryu who used them.

 

Prof K. S. Shukla notes a third recension called the Atharva-jyotisha ascribed to Rshis Svayambhu and Bhrgu which belongs to a later date. This recension, consisting of 162 verses deals with both astronomy and astrology. It mentions the names of the seven grahas and the weekdays. And in addition to tithi, nakshatra and yoga which were already known, it gives the names of the seven karanas of the Hindu calendar.<ref name=":13">K. S. Shukla, [https://www.insa.nic.in/writereaddata/UpLoadedFiles/IJHS/Vol04_1And2_11_KSShukla.pdf Astronomy in ancient and medieval India], Indian Journal of History of Science, Vol.4, Nos. 1-2 (1969), pp.99-106.</ref><blockquote>यथा शिखा मयूराणां नागानां मणयो यथा । तद्वद्वेदाङ्गशास्त्राणां ज्योतिषं (गणितं) मूर्धनि स्थितम् ॥ १९ ॥ (Veda. Jyot. 4)<ref>B.B. Datta and A. N. Singh (1962) ''History of Hindu Mathematics, A Source Book, Parts 1 and 2.'' Bombay: Asia Publishing House. (Page 7)</ref> </blockquote><blockquote>''yathā śikhā mayūrāṇāṁ nāgānāṁ maṇayo yathā । tadvadvedāṅgaśāsrāṇāṁ jyotiṣaṁ (gaṇitaṁ) mūrdhani sthitam ॥ 19 ॥''</blockquote>Like the crests on the heads of peacocks, like the gems on the hoods of the snakes (cobras), astronomy (mathematics) is at the highest position of vedanga shastras (the six ancillary branches of knowledge).

== Contents of Vedanga Jyotisha ==

== Contents of Vedanga Jyotisha ==

The practical way of measuring the time is mentioned as the time taken by a specified quantity of water to flow through the orifice of a specified water-clock as one nadika i.e. 1/60 part of a day.  

The practical way of measuring the time is mentioned as the time taken by a specified quantity of water to flow through the orifice of a specified water-clock as one nadika i.e. 1/60 part of a day.  

A yuga of 5 solar years is mentioned which consists of 67 lunar sidereal cycles, 1830 days, 1835 sidereal days, 62 sinodic months, 1860 tithis, 135 solar nakshatras, 1809 lunar nakshatras and 1768 risings of the Moon. The text also mentions that there are 10 ayanas and 10 vishuvas and 30 rtus in a yuga.<ref name=":1" /> The names of the five years of a yuga being<ref name=":0">Balachandra Rao, S. (2017 Third Edition) Indian Mathematics and Astronomy. Benguluru : Bhavan's Gandhi Center of Science & Human Values</ref>

A yuga of 5 solar years is mentioned which consists of 67 lunar sidereal cycles, 1830 days, 1835 sidereal days, 62 sinodic months, 1860 tithis, 135 solar nakshatras, 1809 lunar nakshatras and 1768 risings of the Moon. The text also mentions that there are 10 ayanas and 10 vishuvas and 30 rtus in a yuga.<ref name=":1" /><ref>Kuppanna Sastry, T. S. and Sarma, K. V. (1985) ''Vedanga Jyotisa of Lagadha in its Rk and Yajus Recensions with the translation and notes of Prof. T. S. Kuppanna Sastry.'' New Delhi : Indian National Science Academy</ref> The names of the five years of a yuga being<ref name=":0">Balachandra Rao, S. (2017 Third Edition) Indian Mathematics and Astronomy. Benguluru : Bhavan's Gandhi Center of Science & Human Values</ref>

#संवत्सरः॥ Samvatsara

#संवत्सरः॥ Samvatsara

#परिवत्सरः ॥ Parivatsara

#परिवत्सरः ॥ Parivatsara

The present day yuga system consisting of the chaturyugas and mahayugas (as seen in puranic references) is discussed under the heading [[Kala (कालः)|Kala]].

The present day yuga system consisting of the chaturyugas and mahayugas (as seen in puranic references) is discussed under the heading [[Kala (कालः)|Kala]].

The Vedic astronomers also noted that the shortest day was at the winter solistice when the seasonal year Shishira began with Uttarayana and rose to a maximum at the summer solistice. A glossary is given to explain the astronomical terms used in this article.

The Vedic astronomers also noted that the shortest day was at the winter solistice when the seasonal year Shishira began with Uttarayana and rose to a maximum at the summer solistice. <blockquote>''However, the Vedanga Jyotisha astronomy suffered from two main defects. Since there are actually 1826.2819 days in a yuga of five solar (sidereal) years and not 1830 as stated in the Vedanga Jyotisha, therefore if one yuga was taken to commence at a winter solstice the next one commenced about four days later than the next winter solstice and not at the next winter solstice. Similarly, since there are actually 1830.8961 days in a period of 62 lunar months and not 1830 as stated in the Vedanga Jyotisha, therefore there was a deficit of about one tithi in the yuga of five solar years. These discrepancies must have been rectified but we do not know when and how this was done.''<ref name=":15" /></blockquote>A glossary is given in the last section to explain the astronomical terms used in this article.

== Siddhantas ==

== Siddhantas ==

According to Prof. Balachandra Rao, the astronomical calculations described in Vedanga Jyotisha were in practical use for a long time. Around the beginning of the Christian era, a new class of Indian Astronomical literature emerged namely the Siddhantas. The word 'siddhanta' has the connotation of an established theory. These siddhanta texts contain much more material and topics than the Vedanga Jyotisha.   

According to Prof. Balachandra Rao, the astronomical calculations described in Vedanga Jyotisha were in practical use for a long time. Around the beginning of the Christian era, a new class of Indian Astronomical literature emerged namely the Siddhantas. The word 'siddhanta' has the connotation of an established theory. These siddhanta texts contain much more material and topics than the Vedanga Jyotisha.   

While nakshatra system was existing, the twelve signs of the zodiac Mesha, Vrshabha etc were introduced. Computations for arriving at the precise values for different aspects such as the length of the solar year, motion of the planets, solar and lunar eclipses, determination ofmean and true positions of planets formed the core content of these siddhantas. Mathematics was greatly developed to aid these calculations.   

While nakshatra system was existing, the twelve signs of the zodiac Mesha, Vrshabha etc were introduced. Computations for arriving at the precise values for different aspects such as the length of the solar year, motion of the grahas, solar and lunar eclipses, determination of mean and true positions of grahas formed the core content of these siddhantas. Mathematics was greatly developed to aid these calculations.   

According to tradition there were principally 18 Siddhantas   

According to tradition there were principally 18 Siddhantas   

# Saunaka}}   

# Saunaka}}   

Among there only five siddhantas were extant during the time of Varahamihira namely, Saura (or Surya) Paitamaha (or Brahma), Vaishishta, Romaka and Paulisa. These five were ably collected by Varahamihira and preserved in his Panchasiddhantika text.   

Among them only five siddhantas were extant during the time of Varahamihira namely, Saura (or Surya) Paitamaha (or Brahma), Vaishishta, Romaka and Paulisa. These five were ably collected by Varahamihira and preserved in his Panchasiddhantika text.   

== Glossary of Astronomical Terms ==

== Glossary of Astronomical Terms ==

{| class="wikitable"

{| class="wikitable"

|-

|-

|Ardharatra : Midnight

|Ardharatra : Midnight

|

|Madhya rekha : Central meridian of the earth passing through Lanka, Ujjaiyini, Kurukshetra, and Mount Meru

|-

|-

|Ayanamsa : Amount of precession of equinoxes (in degrees)

|Ayanamsa : Amount of precession of equinoxes (in degrees)

|

|Madhyahna : Mid day

|-

|-

|Ardharatrika : Calculations from the midnight

|Ardharatrika : Calculations from the midnight

|

|Manda : Slow

|-

|-

|Ayananta : Solistice

|Ayananta : Solistice

|

|Masa : Conjunctions of grahas; yuti, yoga

|-

|-

|Bhachakra : Zodiac (consisting of 27 nakshatras or twelve rashis)

|Bhachakra : Zodiac (consisting of 27 nakshatras or twelve rashis)

|

|Meru : Earth's pole

|-

|-

|Bhagana : Revolutions of a celestial body in a long period of time (like Mahayuga)

|Bhagana : Revolutions of a celestial body in a long period of time (like Mahayuga)

|

|Muhurta : A unit of time; 30 muhurtas = 1 day; 1 muhurta = 2 ghatikas = 48 minutes

|-

|-

|Bhaga : One degree of arc; amsa

|Bhaga : One degree of arc; amsa

|

|Nakshatra dina : Sidereal day

|-

|-

|Bhugola : Terrestrial globe

|Bhugola : Terrestrial globe

|

|Nimesha : A unit of time; according to the siddhanta siromani, 1 day = 9,72,000 nimeshas

|-

|-

|Chakra : Circle, cycle, 360⁰  

|Chakra : Circle, cycle, 360⁰  

|

|Paada : A quarter; quadrant

|-

|-

|Chakramsa : Degrees in a circle, 360⁰  

|Chakramsa : Degrees in a circle, 360⁰  

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|Paksha : Forthnight; half of a lunar month

|-

|-

|Chandrakala : 1/16th of the moon's disc

|Chandrakala : 1/16th of the moon's disc

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|Pala : A unit of time; Vinadi

|-

|-

|Chaturyuga : Great age of 43,20,000 years; Mahayuga

|Chaturyuga : Great age of 43,20,000 years; Mahayuga

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|Praahna : Forenoon; purvahna

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|-

|Chaadya : Eclipsed body ; Graahya

|Chaadya : Eclipsed body ; Graahya

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|Praana : A uit of time; 4 seconds of sidereal time; asu

|-

|-

|Chakralipta : Minutes of arc in a circle; 360⁰ x 60¹ = 21,600¹

|Chakralipta : Minutes of arc in a circle; 360⁰ x 60¹ = 21,600¹

|

|Pratipat : The first tithi (lunar day) of either bright or dark half of a lunar month

|-

|-

|Chandra : The moon

|Chandra : The moon

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|Purnima : Fullmoon; opposition of the sun and the moon

|-

|-

|Chandramasa : The lunar month

|Chandramasa : The lunar month

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|Rahu : Ascending node of the moon; paata of the moon; Tamas

|-

|-

|Chaadaka : Eclipser ; Grahaka

|Chaadaka : Eclipser ; Grahaka

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|Rashi : Zodiacal constellation; each 30⁰ extent

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|-

|Chaaya : Shadow

|Chaaya : Shadow

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|Rtu : Season; a year consists of six rtus

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|-

|Dakshinayana : Southern course of Sun

|Dakshinayana : Southern course of Sun

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|Sauradina : Solar day

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|-

|Darsa : Conjunction of the sun and the moon

|Darsa : Conjunction of the sun and the moon

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|Sauravarsha : Solar year

|-

|-

|Dhruva : Pole Star ; fixed

|Dhruva : Pole Star ; fixed

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|Saavana dina : Civil day; kudina; bhudivasa

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|-

|Dinagana : Civil days; Ahargana

|Dinagana : Civil days; Ahargana

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|Sparshakala : Time of the first contact of an eclipse

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|-

|Dinardha : Half day

|Dinardha : Half day

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|Sraavishta : Dhanishta constellation

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|-

|Gati : Motion

|Gati : Motion

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|Suklapaksha : Bright half of a lunar month

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|-

|Ghana : Cube

|Ghana : Cube

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|Tantra : Indian astronomical texts which adopt the beginning of Kaliyuga as the epoch

|-

|-

|Ghatika : A unit of time; 1/60th part of a day (24 minutes); naadi, nadika, ghati

|Ghatika : A unit of time; 1/60th part of a day (24 minutes); naadi, nadika, ghati

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|Tithi : Lunar day; 1/30th of a lunar month

|-

|-

|Grahana : Eclipse

|Grahana : Eclipse

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|Uttarayana : Northern course of the Sun along the ecliptic

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|-

|Hora : One hour; 1/24th of a day

|Hora : One hour; 1/24th of a day

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|Vikalaa : One second of arc; 1/3600th of a degree; Vilipta, Vilipti

|}

|}