Dunsink Lane, Dublin 15, D15 XR2R

The Armagh-Dunsink-Harvard (ADH) Telescope

The Armagh-Dunsink-Harvard telescope (ADH) was the first major international project undertaken by Dunsink Observatory following the observatory’s re-opening as part of DIAS’ School of Cosmic Physics (founded in 1947).

The ADH was the brainchild of Eric Lindsay, Director of Armagh Observatory, and resulted from the first cooperative agreement between Northern Ireland and Ireland during a period of little communications between the two jurisdictions. He and Harlow Shapley, Director of Harvard Observatory, conceived of a plan to build a “Schmidt” telescope at Boyden to study stars in the southern skies. Lindsay had been at Harvard and Harvard’s Southern Station in Boyden in the 1930s.

Astronomers Bart Bok (Harvard; left) and Eric Lindsay (Armagh; right) with Taoiseach Eamon de Valera circa 1961. Figure from Butler (2007).

A serendipitous encounter between Shapley and Eamon de Valera at Shannon Airport in 1946 gave Shapley the opportunity to tell the then Taoiseach (Irish Prime Minister) of his and Lindsay’s idea. De Valera did not take much convincing as he had recently established the Dublin Institute for Advanced Studies (DIAS) and arranged for Dunsink Observatory to be purchased by the State from Trinity College Dublin and operated by DIAS’s newly formed School of Cosmic Physics. The Armagh-Dunsink-Harvard telescope was an opportunity to develop an international collaborations with Harvard and to build closer links between Northern Ireland and the Republic during a difficult period between the two jurisdictions.

“It was the present writer’s [Lindsay’s] task to bring about the cooperation of the two Irish governments, and on the retuning to Ireland in the spring of 1946 negotiations were entered into with the governments of Northern Ireland and the Republic of Ireland. These negotiations occupied some considerable time, but eventually Mr. de Valera, Prime Minister of the Republic of Ireland, on behalf of his Cabinet, and the late Major J. Maynard Sinclair, Minister of Finance in the Government of N. Ireland, on behalf of the N. Ireland Cabinet, agreed each to allocate the required sum of £5,000.”

Lindsay (1953).

The ADH was a Baker-Schmidt telescope design, giving it a large field-of-view and making it well suited to studying large areas of the southern sky. Indeed, it was the largest Schmidt telescope in the southern hemisphere when constructed in 1950. The primary mirror was made from a 36 inch/0.90 m spherical Pyrex blank that was purchased by Shapely in 1946 for $2,000. Light from the primary was then directed to a 0.43 m spherical secondary and then to the focal plane, where circular photographic plates were then used to capture images. The telescope was manufactured in 1949 by Perkin Elmer Corporation, arriving in Bloemfontein in October 1950.

Optics of the ADH telescope, drawn to scale. From right: 33 inch correcting lens, secondary mirror, photographic plate-holder, 36 inch/90 cm primary mirror. The total length of the telescope tube was 168 inches/4.27 m. From Bok (1952).

A 32 inch diameter objective prism was then added to the ADH in July 1951 to facilitate the use of the telescope for stellar and galactic spectroscopy. Figured by Perkin-Elmer Corporation in the US, the prism was at that time the largest ever manufactured for an astronomical telescope. This full-aperture piece of dispersive glass was placed at the entrance to the telescope, and creating multiple spectra of stars in a very wide field-of-view. Queen’s University Belfast contributed £1,000 towards the cost of the prism, with Harvard making up the remainder.

The tube of the ADH telescope at the Perkin-Elmer Corporation’s works in the US (February 1950). Standing by the telescope (left to right) are: Kevin Rush (Irish Consul in New York), Peter Lindhorse (South African Vice-Consul), John Dawson (British Vice-Consul), Charles Elmer and Richard Perkin (co-founders of Perkin-Elmer Corporation), Harlow Shapley (Director of Harvard Observatory) and Bart Bok (Harvard Observatory). Figure from Butler (2007).

The telescope was initially used in the early 1950s by Harvard astronomers to study the Carina and Sagittarius regions of the southern Milky Way and to make detailed image and spectra of the Magellanic Clouds, while Armagh, Dunsink and others undertook at wide variety of observations including, three-colour imaging of Open Clusters, asteroid searches, spectroscopy of the Coal Sack Nebula, and imaging of the Eta Carinae Nebula. By the mid-1960s, a close collaboration was formed between Dunsink (P. Wayman and C. J., Butler) and Armagh (A. D. Andrews) using the ADH for photographic photometry, the study of Cepheid variables in the Magellanic Clouds and flare stars in Orion. Indeed, this work was facilitated but the development of data analysis techniques on an IBM 1620 computer at Dunsink and on computers at the Northern Irish Ministry of Finance. In the early 1970s, the ADH was used to study the distance to and the age of the southern galactic cluster NGC 3766 and to search for dark nebulae in the Large Magellanic Cloud.

The Large Magellanic Cloud photographed with the ADH telescope. From an article published in Scientific American in 1952 by Bart Bok (Harvard Observatory).

The telescope was gradually supplanted by larger optical telescopes in Australia and Chile and its use was gradually ramped down in the late 1970s. It was finally dismantled and transported to Dunink Observatory for storage in 1981. The primary and secondary mirrors are currently stored in the basement of Dunsink, while the objective prism is on public display in the Board Room of the observatory.

Astronomical links between Dublin and Boyden were re-established in 2005 with the installation of a new Irish telescope at Boyden by Lorraine Hanlon and her team from University College Dublin’s School of Physics (Boyden was actually suggested by Brendan Jordan, Technical Officer at Dunsink Observatory). The Watcher Telescope is a robotic 40 cm Cassegrain telescope and Andor CCD camera system designed to make detailed observations of light that follows the universe’s most powerful explosions called gamma-ray bursts.

UCD’s Watcher Telescope installed at Boyden Observatory in 2005. Photo credit: Antonio Martin Carrillo (UCD).

2022 is the 75th anniversary of the formation of DIAS’ School of Cosmic Physics and the School taking over the running of Dunsink Observatory, so we will certainly be celebrating the ADH and the on-going links between Dunsink, Armagh and our many international partners.

Further details on the ADH can be found in the articles below, while a more complete list of publications can be found on NASA’s Astrophysical Data System.


The Armagh-Dunsink-Harvard Telescope: from dream to oblivion“, Journal of Astronomical History and Heritage, J. Butler, 2007.

The Optical Performance of the 81/90/3032mm ADH Baker-Schmidt Telescope“, A. D. Andrews, 1997.

Classification of ADH Spectra“, Irish Astronomical Journal, F. C. Doyle, C. F. Butler, 1978.

Newly Discovered Clusters of the Large Magellanic Cloud“, Astronomical Journal, P. W. Hodge, 1966.

On the Alignment of the ADH Baker-Schmidt Telescope of the Boyden Observatory“, A. D. Andrews, J. Dommanget, Irish Astronomical Journal, 1965.

Planetary Nebulae in the Large Magellanic Cloud“, Nature, E. M. Lindsay, 1959.

The ADH (Armagh-Dunsink-Harvard) Telescope“, Irish Astronomical Journal, E. M. Lindsay, 1953.

The Southern Sky“, Scientific American, B. Bok, 1952.

An Armagh Dunsink Harvard Telescope“, Nature, E. M. Lindsay, 1947.

Author: Peter T. Gallagher (January, 2022).