The Tantra of Kalachakra is the basis of Tibetan astronomy. It explains some phenomena in a similar manner as modern astronomy science. Hence, Sun eclipse is described as the Moon passing between the Sun and the Earth. In 1318, the 3rd Karmapa received vision of Kalachakra which he used to introduce a revised system of astronomy and astrology named the "Tsurphu Tradition of Astrology" (Tibetan: Tsur-tsi) which is still used in the

Karma Kagyu Karma Kagyu (), or Kamtsang Kagyu (), is a widely practiced and probably the second-largest lineage within the Kagyu school, one of the four major schools of Tibetan Buddhism. The lineage has long-standing monasteries in Tibet, China, Russia, Mon ...

school for the calculation of the

Tibetan calendar The Tibetan calendar (), or Tibetan lunar calendar, is a lunisolar calendar, that is, the Tibetan year is composed of either 12 or 13 lunar months, each beginning and ending with a new moon. A thirteenth month is added every two or three years, s ...

.The Third Gyalwa Karmapa, Rangjung Dorje
site of Karma Lekshey Ling Institute

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Further reading