Bách khoa chiêm tinh–thiên văn khoảng 120 quyển, tập hợp cổ chiêm và lịch pháp trước Đường, gồm cả Cửu Chấp lịch Ấn Độ. Từng cấm truyền, tái phát hiện cuối Minh; là kho nguyên liệu lớn nhất cho chiêm tinh cổ Trung Quốc.
Ứng dụng: Tra chiêm tinh, dị tượng, lịch số và trích dẫn cổ thư đã thất truyền; nền cho các sách quan tượng sau này.
全名《大唐开元占经》，唐太史监瞿昙悉达（印度裔）开元间（约718–726）奉敕主编，一百二十卷。汇辑唐前七十余种天文星占佚书：卷一–二宇宙论（引张衡《灵宪》等），卷三–九十日月五星恒星流彗占，卷九一–一〇二气象占，卷一〇三麟德历，卷一〇四算法与《九执历》（印度九曜），卷一〇五古今历积年。唐后秘藏，明末复出，为保存先秦至唐星占与历算资料的巨型类纂。
⚡ Ứng dụng: 星占分野、天象与人事对应；八字/择日可参古代天文占验框架与九曜观念。
🔗 Liên quan: 乙巳占；观象玩占；灵台秘苑
The Kaiyuan treatise on divination proves that celestial and meteorological signs form a systematic, taxonomic science of correspondence to state and human outcomes—prediction as classified knowledge, not pure inspiration. Exhaustive cataloguing argues that completeness of sign inventory increases reliability of inference. The sky is a readable code with rules of combination, hierarchy, and historical precedent.
1) Build personal '占经' tables: chart pattern → outcome frequency, not only classical quotes. 2) Never read one sign alone; require co-occurrence rules as 开元 does with multi-phenomena. 3) Separate state-level omen logic from private charts—scale mismatch is error. 4) Cultivation: sky-gazing with logbook—train correspondence perception. 5) When modern data contradict a classical line, update the catalog; taxonomy is living.
Unlike biji that prove by sparse anecdote, 开元占经 proves by encyclopedic system. It differs from 徐神翁语录’s mind-stillness emphasis by externalizing authority into sky tables—yet both assume lawful pattern. Why: the Kaiyuan project is imperial completeness; its logic is that missing entries, not missing magic, cause failure.