For the first 150 years of the Observatory’s existence it relied primarily on observations carried out in Ireland in what has often been described as ‘one of the worst astronomical climates in the world’.
It is not just the frequency of cloudy weather that inhibits observations in Ireland, but the constantly changing transparency of the atmosphere. As equipment and techniques of observation have improved the accuracy of the observations became more and more limited by the use of poor quality, low altitude sites.
Since 1950, with the advent of cheap air travel, it has become possible for Armagh astronomers to make observations of high accuracy with telescopes at moderately high altitudes, in dry semi-tropical regions of the world. Often the best quality sites are to be found on volcanic islands in the Pacific or Atlantic Oceans, such as the Canary Islands or the Hawaiian Islands. These new observatories are of an international character, similar to the pioneering Boyden Observatory set up earlier in South Africa. The five observatories most commonly used by astronomers at Armagh are at Hawaii, La Palma in the Canary Islands, the Anglo-Australian Observatory, New South Wales, the European Southern Observatory, Chile and the South African Astronomical Observatory, Cape Province.
During the 1970’s and the 80’s a number of satellites have been launched which are designed specifically to make astronomial observations from above the Earth’s atmosphere. Mostly, these orbiting observatories study the emission of stars and galaxies in parts of the spectrum not accessible from the ground, such as X-rays and the extreme ultraviolet. Astronomers at Armagh Observatory have been making such observations since 1979 when they made the first observation of a flare in the ultraviolet on the dim, nearby star Gliese 867A. Subsequently, Armagh astronomers have employed the European satellite EXOSAT and the Japanese satellite GINGA to make X-ray observations of stars and the NASA satellite SMM to observe the Sun.
