With a view to developing astronomical and astrophysical studies in India as envisaged by the planning committee constituted by the Govt. of India in 1945, a small unit, known as Nautical Almanac Unit, was set up under CSIR at Calcutta. Although the Govt. of India used Gregorian calendar for official use, divergent practices of calendar keeping were in vogue during the period of post independence of the country. A need was felt by the then Prime Minister, Late Pt. Jawaharlal Nehru to develop a unified National Calendar on the basis of the most accurate modern astronomical data in the interest of national integrity. Keeping these in view, a Calendar Reform Committee was formed in 1952 under the CSIR with Late Prof. Meghnad Saha as the Chairman. The Committee recommended preparation of the Indian Ephemeris and Nautical almanac (renamed as Indian Astronomical Ephemeris from 1979 issue) incorporating therein usual astronomical data calculated with most modern astronomical formula and to publish the National Calendar of India (using Saka Era) in the form of Rashtriya Panchang with Solar Calendar system for civil use. It was decided that these works should be done by the Nautical Almanac Unit. This Unit was taken over by the India Meteorological Department from CSIR on 1st December, 1955 and put under Regional Meteorological Centre, Calcutta. On 1st December 1979, following the recommendations of Dr. Ramanna Committee, the centre was made an independent centre and renamed as Positional Astronomy Centre. It was then brought under the direct administrative control of DGM. A Standing Advisory Committee, consisting of eminent experts in the field of astronomy advices DGM on technical matters and future scientific programs of the centre.
PAC compiles and publishes the following important annual publications:
The Indian Astronomical Ephemeris contains over 500 pages of astronomical data on the position of Sun, Moon, Planets, and Bright Stars and a section on the National Calendar of India (Saka Calendar) with the timings of Tithis, Nakshatras etc. and the festival dates. The publication Rashtriya Panchang is a popular publication brought out with the aim of providing a standard unified calendar for the whole country and promoting a scientific basis for Panchang calculation. This publication contains the Indian National Calendar data based on Saka Era as recommended by the Calendar Reform Committee and also All India Sidereal Solar Calendar dates based on Kali Era recommended by the Peer Review Committee along with other usual panchang parameters. PAC brought out an English translation of Bhartiya Jyotish Shastra in two parts from the original Marathi version by late Shri S.B. Dixit, which is a pioneering work on the history of ancient and medieval Indian Astronomy.
The Centre meets the data requirements of a large number of users including Govt. organizations, non Govt. organizations, professional astronomers, research scholars, various panchang makers, general public etc.
Lunar data for prediction of tides are computed for the Survey of India and data of the Sun’s daily path are useful to civil engineers, architects and telecommunications engineers. PAC provides data for determining the dates of festivals of all communities in India in advance for holiday declaration by the Government, tourist promotion abroad and for use of Panchang Makers.
The centre also acts as national agency for attending all matters concerning to calendars. This centre also provides five years advance accurate calendric data to many leading panchang makers of the country for preparation of their own Panchangs.
The centre also contributes to a great extent in popularizing astronomy through publication of monthly astronomical bulletin and star charts, organizing different public outreach programme on different astronomical events, issuing press release from time to time and attending live discussions on various electronic media etc on different astronomical events.
This centre also takes observation on special astronomical events from time to time with the help of its portable telescopes at different places of the country.
PAC organizes special observation camp for astronomical and meteorological observations during Total Solar Eclipse when visible in India. It also publishes advance information related to both solar and lunar eclipses, including climatological data which are important for eclipse viewing purposes.