How to read the atlas
Time runs left → right (500 BCE → 1750 CE, linear, labelled every century with lighter 50-year lines). Vertical rows are centres and schools of astronomical work — Kusumapura, Bhillamāla, Ujjain, the commentator lineage, Kāśī, and Kerala — plus a top row for the Vedic and Siddhāntic inheritance the tradition grew from and a bottom row for the political and cross-cultural currents that shaped it. Each glyph sits at its event's date on its centre's row; bars are people, showing the years an astronomer was active.
Two dashed teal lines mark transmission: Greek and Babylonian astronomy entering India around 150 CE on the traditional dating (the Yavanajātaka), and Indian planetary methods travelling out to Baghdad around 770 CE, where they seeded the Arabic zīj tradition of Volume II. Dates are Common Era on the axis; each card also gives the Śaka-era year (Śaka = CE − 78), the era most of these astronomers actually dated by.
Glyph shape is the kind of contribution: filled circle = observation or discovery, open circle = treatise or table, square = founding of an institution, triangle = instrument or technique, diamond = political or dynastic event. Glyph fill colour matches the centre's stripe.
The centres, briefly
Three threads that make this more than a list
The first is the siddhānta — the systematic astronomical treatise in Sanskrit verse. From the lost early Siddhāntas digested in Varāhamihira's Pañcasiddhāntikā, through Āryabhaṭa's Āryabhaṭīya, Brahmagupta's Brāhmasphuṭasiddhānta, and Bhāskara II's Siddhāntaśiromaṇi, the treatise and its terse verse form carried Indian astronomy for a thousand years — and its numerals and its sine function carried it to the world.
The second is the infinite series. Two and a half centuries before the European calculus, Mādhava of Saṅgamagrāma and the Kerala school derived convergent power series for π, sine, and cosine, and — in Jyeṣṭhadeva's Yuktibhāṣā — wrote out their derivations, arguably the first calculus text. Whether any of this reached Europe is unproven and much debated; the results and their proofs are on this atlas, and the reader can weigh them.
The third is exchange. India was a hub, not an island: it received Hellenistic and Babylonian astronomy (the zodiac, the horoscope) and sent its own siddhāntas to Baghdad, where al-Fazārī's Zīj al-Sindhind begins Volume II. Al-Bīrūnī came to learn Sanskrit; Jai Singh later gathered Hindu, Islamic, and European astronomy into a single program. The tradition is best read alongside its neighbours, not apart from them.
Methodology — what counts, what does not
Inclusion. An entry qualifies if (a) the work was done within the Indian (Sanskritic and regional-language) astronomical tradition between roughly 500 BCE and 1750 CE, and (b) it was a primary contribution to astronomy or mathematical astronomy, its instrumentation, or the institutional infrastructure of observation. The mathematics is included where it served the astronomy — as almost all of it did: trigonometry, the numerals, and the series were developed by astronomers, for computing the heavens.
Astronomy and jyotiṣa. In Sanskrit, jyotiṣa covers both mathematical astronomy (gaṇita / gola) and astrology (horā). This atlas catalogues the former: computation of positions, calendars, eclipses, and instruments. Astrological prognostication is not treated as astronomy, though the courtly demand for it (and the shared texts) is noted where it bears on the observational record.
Sources and dating. Every card cites a primary text or a modern critical edition, with transliteration in a light IAST scheme. Dates follow the standard reference literature (Pingree's Census of the Exact Sciences in Sanskrit, Plofker's Mathematics in India, and the critical editions of Shukla & Sarma, Ramasubramanian & Sriram). Where a date or attribution is contested — and for the earliest material it often is — the card says so.
On the calculus-transmission question. The Kerala series are securely dated and securely Indian. Whether knowledge of them reached seventeenth-century Europe is a separate, unresolved question; this atlas presents the Indian achievement on its own terms and flags the transmission claim as open rather than asserting it.
Companion RAVEN material
The Indian sine table (jyā, the ancestor — via Arabic jayb — of the very word "sine") and the decimal place-value numerals are upstream of every computation in the RAVEN Catalogs and Foundations. The Siddhānta that reached Baghdad around 770 is among the opening entries of Volume II — Astronomy by Islamic Hands, making these two volumes literally continuous at that seam. And Jai Singh's Jantar Mantar program closes a loop with Volume I: he sent a Jesuit mission to Europe and used the tables of the French astronomer Philippe de La Hire, so the three volumes meet in his eighteenth-century Jaipur.