The Surya Siddhanta, an Indian astronomical text written in the 4th or 5th century CE, had a significant influence on Celtic astronomy.

The Surya Siddhanta introduced several important concepts to Celtic astronomy, including the concept of zero, the use of the zodiac, and the calculation of eclipses.

The introduction of the concept of zero had a profound impact on Celtic astronomy, allowing for more accurate calculations, simplifying astronomical calculations, and enabling the development of new astronomical instruments.

The use of the zodiac in Celtic astronomy had multiple significances, including allowing for the tracking of the movement of the sun and moon, enabling the prediction of eclipses, and helping in understanding the seasons and their impact on agriculture.

The Surya Siddhanta contributed to the development of the Celtic calendar in several ways, including introducing the concept of intercalation, providing a method for calculating the length of the year, and helping in determining the dates of important festivals and events.

The Coligny Calendar, a bronze tablet discovered in France, is believed to have been influenced by Indian astronomy.

The Coligny Calendar was a versatile instrument that served multiple purposes, including tracking the movement of the sun and moon, predicting eclipses, and determining the dates of important festivals and events.

Indian astronomy played a role in influencing the construction of Celtic megalithic structures by helping in determining the orientation of the structures, providing insights into the celestial events that were significant to the Celts, and enabling them to align their structures with specific stars or constellations.

The Indian concept of samsara, the cycle of birth, death, and rebirth, influenced the Celtic belief in reincarnation.

The Indian concept of samsara had a profound impact on Celtic mythology and folklore, leading to the development of stories about heroes and their journeys to the Otherworld, influencing the Celtic belief in the importance of honoring ancestors, and contributing to the Celtic tradition of storytelling and oral history.

The Celtic festival of Samhain, marking the end of the harvest season and the beginning of winter, was influenced by Indian astronomy.

Indian astronomy influenced the Celtic celebration of Samhain in multiple ways, including helping in determining the exact date of the festival, providing insights into the celestial events associated with the festival, and influencing the rituals and traditions associated with the festival.

The Celtic god Lugh was associated with astronomy and celestial events.

The god Lugh was connected to astronomy and celestial events in multiple ways: he was believed to be the god of the sun, he was associated with the festival of Samhain, and he was credited with inventing the Celtic calendar.

The overall impact of Indian astronomy on Celtic astronomy was significant, leading to the development of new astronomical instruments, influencing the Celtic calendar and festivals, and contributing to the Celtic belief in reincarnation and the importance of honoring ancestors.