04-19-2004, 07:36 PM
Names of Stars from the Period of Vedas
S. Balakrishna, Ph.D
January 1998
<b>Introduction:</b>
A clear night sky with bright stars is and has always been an object of fascination for mankind. One can probably see about 10,000 stars though millions exist. In this computer era, humans have lost the awe of the objects in the sky due to astonishing advances in science through modern astronomy, human visits to Moon, remote robotic visions of Mars, and views of galaxies through the Hubble telescope. Humans feel a sense of control and omnipotence about their future. However astronomical events listed below makes one wonder.
The Shoemaker-Levy cometâs earth size impact on Jupiter in 1994
the Siberian comet impact of 1908's
The alleged comet impact on the Yucatan Peninsula in Mexico resulting in extinction of Dinosaurs.
The helplessness and insignificance of human power in the face of even minor cosmic events becomes apparent. These events put in to perspective the historical respect and reverence past human societies have had for possible devastation from the sky.
Observation of precise cyclic movement of bodies in the skies formed the basis for calendars and almanacs throughout human history. Relation of apparent motion of Sun, Moon, planets and stars observed from earth, to the solar year with its different seasons controlling weather and agriculture was well known to most older societies (Ref-9). Many societies independently fitted the observed heavenly body motion in to different almanacs with major religious and cultural components in the past. Some are known and certainly many are lost. Even today, such almanacs exist and are used for religious and cultural identity. These almanacs are solar pointer, lunar pointer or a combination of these types. Amongst these, the European Julian solar calendar system modified by Rome's pope Gregory in October 1582 AD, has displaced all other almanacs and is in universal use throughout the world presently. The Gregorian calendar has no lunar components whatsoever.
<span style='color:red'>In the vedic literature, Bharateeya's have the oldest continuing culture running for thousands of years. Pre-vedic culture understood the motions of the bodies in skies and evolved a moon pointer calendar, moon pointing to daily stars in the skies. Various stars in the moon path and a few others were given proper names many thousand years ago. Some notable proper names from veda's assigned to stars are the 27 or 28 daily stars Ashwini to Revati, the saptarishis (Ursa major for Rishis Marichi,Vasishta,Angirasa,Atri,Puslastya,Pulaha,Karatu or Gautama, Bhardwaja, Vishvamitra, Kashyapa, Jamdagni, Vasishtha and Atri), Dhruva (Polaris) and Arundhati. Chandramana or Moon pointer almanac has been extensively used during and since Vedic period. The thousands of year old lunar almanac system is an integral part of traditional Bharateeyaâs, who probably have a birth horoscope where in an important parameter is the birth Nakshatra and birth Rashi. While many Bharateeyaâs know that nakshatra's refer to objects in the sky, not many can point to the night sky and identify these Nakshatra's by their names. </span>
This article aims identify the Nakshatraâs referred to by Bharateeya vedic culture, and to provide present day alternate names from other cultures, including modern astronomical identities from star catalogs.
<b>Bharateeya Nakshatra System: </b>
<span style='font-size:14pt;line-height:100%'>Though the lunar time between two successive full moons is 29.53059 solar days, the time taken for moon to go round the earth (sidereal month) is 27.32166 days. Moon also has an oscillatory motion crossing the ecliptic. The moon anomalistic motion and nodal motion have periods are 27.55545 and 27.21222 days for a revolution around earth. The reason for time between full moons being higher than sidereal month is because, the moon has to go around the earth by more than a revolution (nearly 390 degrees) to keep with earth which moves forward in its trajectory around sun. The Chandramaana lunar calendar system keeps a natural cyclic count of days using two Moon based properties described below. </span>
<span style='font-size:14pt;line-height:100%'>First property is that moon functions as an astronomical day count clock in which Moon is the pointer and the stars are numerals in the sky pointed to by moon each day of the lunar month. The astronomers of Vedic period identified this approximate 13 degree movement of the moon between successive days and named the 27/28 stars pointed to by moon on a daily basis over a rotation as 27/28 nakshatra's, corresponding to little less than a lunar month. Thus a Nakshatra shift corresponds to moon traverse over approximately one solar day.
The second property is the size of fractional moon exposure to sun can indicate a day count and is defined as a moon day or thiti. Thirty thiti's are defined in a lunar month, each thiti being smaller than a solar day. Fifteen are identified as Shukla paksha or ascending fortnight and next fifteen are called krishna paksha or descending fortnight.
This system of day count calendar keeping, is traceable to Veda's. Veda's, which are perhaps the oldest original documentation of knowledge any where in the world, still in their original shape and language. A study of the Veda's, Brahmana's, and Aaranyaka's point exclusive use of a lunar pointer as the primary calendar in the Vedic periods. Pournamsya, a time at which earth, sun, moon are aligned is a time of singularity used for religious purposes and formed the unit of half a month and is used in Rigveda. The Vedas also refer to solar events such as Aayanas, and Vishuwat-Sankramana's as solar singular events. Ayana means Solstices when apparent North-South movement of Sun reverses, usually occurring on June 21 and Dec 22. Vishuwat means equal or the spring and fall equinoxâs when daytime is equal to nighttime, usually occurring on March 21 and Sep 21. There are vedic references to solar singularities with corresponding solar/lunar pointed star locations.
The six-season definition is unique to vedic system and is not found in any other recorded culture or system. These seasons are, Vasanta, Geeshma, Varsha, Sharad, Himavanta and Shishira each season being about two moon cycles. It is in Taittareeya Samhita (Krishna Yajurveda) and in Atharva samhita 19th kaanda /7th Sootra that an explicit first definition and identification of the twenty- seven(28) Nakshatraâs is available (Refs, 1 and 2). It should be noted that the concept of Zodiac/Raashi is not even hinted in any vedic texts of the old period. </span>
The table below provides a list of the twenty-seven stars from Taittareeya Samhita and Krishna Yajurveda 4th Kaanda 4th Prashna of Andhra School. Similar list is referred to in Atharvaveda, 19th kaanda/7th Sookta. It differs from the Yajurveda list in that twenty eight stars are listed. In 19th Kaanda/8th sooktha twenty eight(ashtha vimshaani) nakshatras are declared. The nakshatra not explicitly used in Jyotishya and in yajurveda is named Abhijit. The taiaareeya brahmana (third Ashtaka) derived from yajurveda again lists 28 nakshatras including Abhijit. It is referred to in Athrvana veda. The author or Drashtaara of Atharva veda sookta is Gaargya Rishi.
The confusion about 27/28 Nakshatras can be analyzed as follows. The 27.3 days taken by moon for visiting the same star can be rounded to either 27 or 28. Each of these integers represents a nakshatra or a daily star. It is possible that initially 28 nakshatras were proposed and defined to represent every day. This is evident from Gargyaâs Nakshtara sooktha. Subsequently many years later when Jyotishya was taking a more formal and mathematical shape, 27 integer identities were perhaps found to be more reasonable and accurate. Hence one of the original 28 nakshatras had to be deleted. This could not be done easily as the vedas are considered to be âapourusheyaâ and no liberties were allowed. Hence perhaps Abhijit, was declared to be an imaginary nakshatra meant only for phala.(ref 10).
The Table below lists names of Nakshatras, the deity to which Nakshatra is dedicated to, and alternate names. Ashwini and Bharani are listed as last two Nakshatras. Note that the list starts from Krittika and not from Ashwini as is currently used in Jyotishya Shaastra (Ref 3). The time at which Rishi Gargya documented the list of nakshatra's in Atharvana Veda is at least circa 2400 BC, as analyzed in appendix I. The appendix also dates the Jyotishya Shaastra as having been brought in to the present form around circa 400 BC.
Nakshatra No. of stars Alternate name Dedicated to
Krittika 6 Agni
Rohini 5 Prajaapati
Mrigasheerisham 3 Soma
Aardharaa 1 Rudra
Punarvasu 2-4 Aditi
Tishya 3 Pushya Brihaspati
Aaslesha 1 Ashresha Sarpa
Maghaa 5 Pitru
Poorva Phalguni 2 Pubba Bhaga
Uttara Phalguni 2 Uttara
Hastaa 3 Savitru
Chitra 1 Chitta Indra
Swati 1 Vaayu
Vishaaka 2 Indraagni
Anooradha 4 Mitra
Jyeshta 3 Indra
Vichruta 11 Moola Pitru
Aashada 2 Purvashada Aapah
Aashada(Abhijit) 3 Uttarashada Vishvedeva
Shrona 3 Shravana Vishnu
Shravishta 4 Dhanishta Vasu
ShathaBhishaja 100 Indra
Proshtapada 2 Purvabhadra
Proshtapada 2 Uttarabhadra Ahirbadhni
Revathi 32 Pausha
Ashwini 3 Ashwini
Bharani 3 Yama
The lunar calendar was in universal and secular use in ancient Bhaarata. Historical events used lunar calendar for dating all events. It is well known that Gautama Buddha was born, achieved his enlightenment and died on full moon day with the full moon pointing to Vishakha Nakshatra. The twelve months were named after the stars at which full moon occurs and these are Chaitra, Vaishakha, Jyeshta, Ashaada, Sharavna, Bhadrapda, Ashwija, Kaartika, Margashira, Pushya, Maagha, Phalguna. Typically alternate stars with some skips refer to month names and hence accommodate 27 stars corresponding to nearly 360 degrees motion of Sun in a solar year. The first question that arises is whether a 'Nakshatra' corresponds to one single star entity or a group of stars in the sky. Bharateeya Jyotishya shaastra states that each Nakshatra name corresponds to a group of stars called star mansions or Asterisms. The concept is that Chandra or Moon visits these mansions in his trajectory around earth. It is very possible that at the inception of daily star concept during the early vedic period, a Nakshatra may have been a specific single star. Nakshatra positions may have been rationalized in later days to mansions or groups of stars for purposes of mathematical averaging to be exactly 13.333 degrees apart required in Jyotishya. The table above also shows the number of stars, accepted by Jyotishya shaastra, constituting the specific Nakshatra.
European Influence on the Bharatheeya system:
The European view (originally from Chaldian and Kassarian cultures of Middle East and from Egypt), propagated by Greek philosophers, of the night sky and the star system ran in a different direction in ancient times in that Sun was considered as the pointer to skies. In contrast, the moon is considered to be the primary pointer from vedic astronomical point of view. Star groups pointed to by the sun were defined as Zodiacs representing clusters of stars forming shapes of animals and figures. Zodiacs were named after animal shapes or Greek mythological figures. The twelve months were named and represented Zodiac groups, which had an animal form through which the Sun passes.
If we compare the names of Bhaarateeya Rashis and Zodiacs and Weekdays, are same but for the language as shown in table below. It is inconceivable that two non-communicating societies can evolve name systems, which are translations of each other in a linguistic sense. Clearly, one of the two parties influenced the other.
Mesha Aries
Vrishabha Taurus
Mithuna Gemini
Karkataka Cancer
Simha Leo
Kanya Virgo
Tula Libra
Vrishchika Scorpio
Dhanu Sagitarrius
Makara Capricorn
Kumbha Aquarius
Meena Pisces
The Vedas and other older texts do not refer to weekdays named after Graha's or Planets or to Raashis. The Grahas referred to in Veda's are Surya, Chandra, Brihaspati, Shukra, Budha, shani, Kuja, Rahu, Ketu. They extensively refer to Nakshatra month names and moon pointing at different Nakshatra's for various purposes. Therefore it appears likely that the Bharateeya cosmological system interacted with the European solar calendar and gradually the Jyotishya shaastra was modified to the present form, as we know now. Sun based concepts of Rashi, weekdays were invoked in to Jyotishya. This could have occurred, perhaps through contact with Yavanas (Greek's) as there is considerable evidence of Greek and Bharateeya interaction during period before Chandra Gupta. Appendix provides astronomical time markers which confirm the origins of Jyotishya Shaastra in present form to circa 400 BC. Without acceptance of this interaction, it is difficult to explain why the twelve Zodiacs of the European star system are translations of the Nakshatra-Rashi defined in Jyotishya.
It is worth while looking at the some Bharateeya astronomers of a more recent time of 300-500 AD. They are Aryabhata, Varaha Mihira, Brahma Gupta. These astronomers were aware of the vedic astronomy and made new and unique contributions. Specifically Aryabhata made contributions to Spherical geometry, a part of understanding the earth as a globe. Varaha Mihira's contributions include pesently used Soorya Siddhanta, (He refers to nine types of time keeping and calenders) and the fact that he proposed Prime Meridian through Ujjain in Madhya Pradesh. He knew of Earth's Precession and called it as ayanaamsha. Brahma Gupta made contributions to Arcsin in Trigonometry. Aryabhata had estimated the beginning of kaliyuga as 3102 BC. He stated that when he was 26, sixty of the 60-year cycles were completed after start of kaliyuga. Varahmihira made an estimate of 2526 before start of Shaka varsha for Mahabharata's Yudhishtira. Texts from that period like Yavana Jataka, Romaka Siddahnta provide evidence of understanding of European astronomical works.
The Chandramaana Lunar scale has 27 daily and twelve month name definitions. While amalgamating the solar calibrations of zodiacs in to Lunar calibrations of Nakshatra's, the issue of translating 27 Nakshatras in a revolution to 12 Rashis was solved in Jyotishya Shaastra by treating 1/4 of a Nakshatra as a unit making Nine quarters of Nakshatra as one Raashi....
S. Balakrishna, Ph.D
January 1998
<b>Introduction:</b>
A clear night sky with bright stars is and has always been an object of fascination for mankind. One can probably see about 10,000 stars though millions exist. In this computer era, humans have lost the awe of the objects in the sky due to astonishing advances in science through modern astronomy, human visits to Moon, remote robotic visions of Mars, and views of galaxies through the Hubble telescope. Humans feel a sense of control and omnipotence about their future. However astronomical events listed below makes one wonder.
The Shoemaker-Levy cometâs earth size impact on Jupiter in 1994
the Siberian comet impact of 1908's
The alleged comet impact on the Yucatan Peninsula in Mexico resulting in extinction of Dinosaurs.
The helplessness and insignificance of human power in the face of even minor cosmic events becomes apparent. These events put in to perspective the historical respect and reverence past human societies have had for possible devastation from the sky.
Observation of precise cyclic movement of bodies in the skies formed the basis for calendars and almanacs throughout human history. Relation of apparent motion of Sun, Moon, planets and stars observed from earth, to the solar year with its different seasons controlling weather and agriculture was well known to most older societies (Ref-9). Many societies independently fitted the observed heavenly body motion in to different almanacs with major religious and cultural components in the past. Some are known and certainly many are lost. Even today, such almanacs exist and are used for religious and cultural identity. These almanacs are solar pointer, lunar pointer or a combination of these types. Amongst these, the European Julian solar calendar system modified by Rome's pope Gregory in October 1582 AD, has displaced all other almanacs and is in universal use throughout the world presently. The Gregorian calendar has no lunar components whatsoever.
<span style='color:red'>In the vedic literature, Bharateeya's have the oldest continuing culture running for thousands of years. Pre-vedic culture understood the motions of the bodies in skies and evolved a moon pointer calendar, moon pointing to daily stars in the skies. Various stars in the moon path and a few others were given proper names many thousand years ago. Some notable proper names from veda's assigned to stars are the 27 or 28 daily stars Ashwini to Revati, the saptarishis (Ursa major for Rishis Marichi,Vasishta,Angirasa,Atri,Puslastya,Pulaha,Karatu or Gautama, Bhardwaja, Vishvamitra, Kashyapa, Jamdagni, Vasishtha and Atri), Dhruva (Polaris) and Arundhati. Chandramana or Moon pointer almanac has been extensively used during and since Vedic period. The thousands of year old lunar almanac system is an integral part of traditional Bharateeyaâs, who probably have a birth horoscope where in an important parameter is the birth Nakshatra and birth Rashi. While many Bharateeyaâs know that nakshatra's refer to objects in the sky, not many can point to the night sky and identify these Nakshatra's by their names. </span>
This article aims identify the Nakshatraâs referred to by Bharateeya vedic culture, and to provide present day alternate names from other cultures, including modern astronomical identities from star catalogs.
<b>Bharateeya Nakshatra System: </b>
<span style='font-size:14pt;line-height:100%'>Though the lunar time between two successive full moons is 29.53059 solar days, the time taken for moon to go round the earth (sidereal month) is 27.32166 days. Moon also has an oscillatory motion crossing the ecliptic. The moon anomalistic motion and nodal motion have periods are 27.55545 and 27.21222 days for a revolution around earth. The reason for time between full moons being higher than sidereal month is because, the moon has to go around the earth by more than a revolution (nearly 390 degrees) to keep with earth which moves forward in its trajectory around sun. The Chandramaana lunar calendar system keeps a natural cyclic count of days using two Moon based properties described below. </span>
<span style='font-size:14pt;line-height:100%'>First property is that moon functions as an astronomical day count clock in which Moon is the pointer and the stars are numerals in the sky pointed to by moon each day of the lunar month. The astronomers of Vedic period identified this approximate 13 degree movement of the moon between successive days and named the 27/28 stars pointed to by moon on a daily basis over a rotation as 27/28 nakshatra's, corresponding to little less than a lunar month. Thus a Nakshatra shift corresponds to moon traverse over approximately one solar day.
The second property is the size of fractional moon exposure to sun can indicate a day count and is defined as a moon day or thiti. Thirty thiti's are defined in a lunar month, each thiti being smaller than a solar day. Fifteen are identified as Shukla paksha or ascending fortnight and next fifteen are called krishna paksha or descending fortnight.
This system of day count calendar keeping, is traceable to Veda's. Veda's, which are perhaps the oldest original documentation of knowledge any where in the world, still in their original shape and language. A study of the Veda's, Brahmana's, and Aaranyaka's point exclusive use of a lunar pointer as the primary calendar in the Vedic periods. Pournamsya, a time at which earth, sun, moon are aligned is a time of singularity used for religious purposes and formed the unit of half a month and is used in Rigveda. The Vedas also refer to solar events such as Aayanas, and Vishuwat-Sankramana's as solar singular events. Ayana means Solstices when apparent North-South movement of Sun reverses, usually occurring on June 21 and Dec 22. Vishuwat means equal or the spring and fall equinoxâs when daytime is equal to nighttime, usually occurring on March 21 and Sep 21. There are vedic references to solar singularities with corresponding solar/lunar pointed star locations.
The six-season definition is unique to vedic system and is not found in any other recorded culture or system. These seasons are, Vasanta, Geeshma, Varsha, Sharad, Himavanta and Shishira each season being about two moon cycles. It is in Taittareeya Samhita (Krishna Yajurveda) and in Atharva samhita 19th kaanda /7th Sootra that an explicit first definition and identification of the twenty- seven(28) Nakshatraâs is available (Refs, 1 and 2). It should be noted that the concept of Zodiac/Raashi is not even hinted in any vedic texts of the old period. </span>
The table below provides a list of the twenty-seven stars from Taittareeya Samhita and Krishna Yajurveda 4th Kaanda 4th Prashna of Andhra School. Similar list is referred to in Atharvaveda, 19th kaanda/7th Sookta. It differs from the Yajurveda list in that twenty eight stars are listed. In 19th Kaanda/8th sooktha twenty eight(ashtha vimshaani) nakshatras are declared. The nakshatra not explicitly used in Jyotishya and in yajurveda is named Abhijit. The taiaareeya brahmana (third Ashtaka) derived from yajurveda again lists 28 nakshatras including Abhijit. It is referred to in Athrvana veda. The author or Drashtaara of Atharva veda sookta is Gaargya Rishi.
The confusion about 27/28 Nakshatras can be analyzed as follows. The 27.3 days taken by moon for visiting the same star can be rounded to either 27 or 28. Each of these integers represents a nakshatra or a daily star. It is possible that initially 28 nakshatras were proposed and defined to represent every day. This is evident from Gargyaâs Nakshtara sooktha. Subsequently many years later when Jyotishya was taking a more formal and mathematical shape, 27 integer identities were perhaps found to be more reasonable and accurate. Hence one of the original 28 nakshatras had to be deleted. This could not be done easily as the vedas are considered to be âapourusheyaâ and no liberties were allowed. Hence perhaps Abhijit, was declared to be an imaginary nakshatra meant only for phala.(ref 10).
The Table below lists names of Nakshatras, the deity to which Nakshatra is dedicated to, and alternate names. Ashwini and Bharani are listed as last two Nakshatras. Note that the list starts from Krittika and not from Ashwini as is currently used in Jyotishya Shaastra (Ref 3). The time at which Rishi Gargya documented the list of nakshatra's in Atharvana Veda is at least circa 2400 BC, as analyzed in appendix I. The appendix also dates the Jyotishya Shaastra as having been brought in to the present form around circa 400 BC.
Nakshatra No. of stars Alternate name Dedicated to
Krittika 6 Agni
Rohini 5 Prajaapati
Mrigasheerisham 3 Soma
Aardharaa 1 Rudra
Punarvasu 2-4 Aditi
Tishya 3 Pushya Brihaspati
Aaslesha 1 Ashresha Sarpa
Maghaa 5 Pitru
Poorva Phalguni 2 Pubba Bhaga
Uttara Phalguni 2 Uttara
Hastaa 3 Savitru
Chitra 1 Chitta Indra
Swati 1 Vaayu
Vishaaka 2 Indraagni
Anooradha 4 Mitra
Jyeshta 3 Indra
Vichruta 11 Moola Pitru
Aashada 2 Purvashada Aapah
Aashada(Abhijit) 3 Uttarashada Vishvedeva
Shrona 3 Shravana Vishnu
Shravishta 4 Dhanishta Vasu
ShathaBhishaja 100 Indra
Proshtapada 2 Purvabhadra
Proshtapada 2 Uttarabhadra Ahirbadhni
Revathi 32 Pausha
Ashwini 3 Ashwini
Bharani 3 Yama
The lunar calendar was in universal and secular use in ancient Bhaarata. Historical events used lunar calendar for dating all events. It is well known that Gautama Buddha was born, achieved his enlightenment and died on full moon day with the full moon pointing to Vishakha Nakshatra. The twelve months were named after the stars at which full moon occurs and these are Chaitra, Vaishakha, Jyeshta, Ashaada, Sharavna, Bhadrapda, Ashwija, Kaartika, Margashira, Pushya, Maagha, Phalguna. Typically alternate stars with some skips refer to month names and hence accommodate 27 stars corresponding to nearly 360 degrees motion of Sun in a solar year. The first question that arises is whether a 'Nakshatra' corresponds to one single star entity or a group of stars in the sky. Bharateeya Jyotishya shaastra states that each Nakshatra name corresponds to a group of stars called star mansions or Asterisms. The concept is that Chandra or Moon visits these mansions in his trajectory around earth. It is very possible that at the inception of daily star concept during the early vedic period, a Nakshatra may have been a specific single star. Nakshatra positions may have been rationalized in later days to mansions or groups of stars for purposes of mathematical averaging to be exactly 13.333 degrees apart required in Jyotishya. The table above also shows the number of stars, accepted by Jyotishya shaastra, constituting the specific Nakshatra.
European Influence on the Bharatheeya system:
The European view (originally from Chaldian and Kassarian cultures of Middle East and from Egypt), propagated by Greek philosophers, of the night sky and the star system ran in a different direction in ancient times in that Sun was considered as the pointer to skies. In contrast, the moon is considered to be the primary pointer from vedic astronomical point of view. Star groups pointed to by the sun were defined as Zodiacs representing clusters of stars forming shapes of animals and figures. Zodiacs were named after animal shapes or Greek mythological figures. The twelve months were named and represented Zodiac groups, which had an animal form through which the Sun passes.
If we compare the names of Bhaarateeya Rashis and Zodiacs and Weekdays, are same but for the language as shown in table below. It is inconceivable that two non-communicating societies can evolve name systems, which are translations of each other in a linguistic sense. Clearly, one of the two parties influenced the other.
- Ravivar Sunday Sun
Induvasar or Somavar Monday Moon
Bhomyavasar or Mangalvar Tuesday Mars
Sowmyavasara orBudhavar Wednesday Mercury
Brihaspativasara or Guruvar Thursday Jupiter
Bhargava vasara or Shukravar Friday Venus
Sthiravasara or Shanivar Saturday Saturn</li>
Mesha Aries
Vrishabha Taurus
Mithuna Gemini
Karkataka Cancer
Simha Leo
Kanya Virgo
Tula Libra
Vrishchika Scorpio
Dhanu Sagitarrius
Makara Capricorn
Kumbha Aquarius
Meena Pisces
The Vedas and other older texts do not refer to weekdays named after Graha's or Planets or to Raashis. The Grahas referred to in Veda's are Surya, Chandra, Brihaspati, Shukra, Budha, shani, Kuja, Rahu, Ketu. They extensively refer to Nakshatra month names and moon pointing at different Nakshatra's for various purposes. Therefore it appears likely that the Bharateeya cosmological system interacted with the European solar calendar and gradually the Jyotishya shaastra was modified to the present form, as we know now. Sun based concepts of Rashi, weekdays were invoked in to Jyotishya. This could have occurred, perhaps through contact with Yavanas (Greek's) as there is considerable evidence of Greek and Bharateeya interaction during period before Chandra Gupta. Appendix provides astronomical time markers which confirm the origins of Jyotishya Shaastra in present form to circa 400 BC. Without acceptance of this interaction, it is difficult to explain why the twelve Zodiacs of the European star system are translations of the Nakshatra-Rashi defined in Jyotishya.
It is worth while looking at the some Bharateeya astronomers of a more recent time of 300-500 AD. They are Aryabhata, Varaha Mihira, Brahma Gupta. These astronomers were aware of the vedic astronomy and made new and unique contributions. Specifically Aryabhata made contributions to Spherical geometry, a part of understanding the earth as a globe. Varaha Mihira's contributions include pesently used Soorya Siddhanta, (He refers to nine types of time keeping and calenders) and the fact that he proposed Prime Meridian through Ujjain in Madhya Pradesh. He knew of Earth's Precession and called it as ayanaamsha. Brahma Gupta made contributions to Arcsin in Trigonometry. Aryabhata had estimated the beginning of kaliyuga as 3102 BC. He stated that when he was 26, sixty of the 60-year cycles were completed after start of kaliyuga. Varahmihira made an estimate of 2526 before start of Shaka varsha for Mahabharata's Yudhishtira. Texts from that period like Yavana Jataka, Romaka Siddahnta provide evidence of understanding of European astronomical works.
The Chandramaana Lunar scale has 27 daily and twelve month name definitions. While amalgamating the solar calibrations of zodiacs in to Lunar calibrations of Nakshatra's, the issue of translating 27 Nakshatras in a revolution to 12 Rashis was solved in Jyotishya Shaastra by treating 1/4 of a Nakshatra as a unit making Nine quarters of Nakshatra as one Raashi....