Telescope:13-inch Astrographic Refractor (1890)

The Astrographic Refractor at Greenwich. Photo by the London Stereoscopic and Photographic Company. Known to have been published in Pearson's Magazine in 1896, this higher quality reproduction is taken from the Greenwich Astrographic Catalogue, Volume 1, (HMSO, 1904)

Ordered in 1888 and delivered in 1890, the 13-inch Astrographic Refractor was one of a number of similar telescopes that were commissioned around that time to take part of an international project to produce a photographic map of the sky (Carte du Ciel).

Made by Sir Howard Grubb of Dublin, it consisted of a 13-inch photographic refractor with a focal length of about 11 feet 3 inches (3.43m), firmly connected to a parallel 10-inch visual guiding telescope of the same focal length on a German Equatorial mount. It also had a 3-inch guiding telescope. The Astrographic Refractor contributed to both the Carte du Ciel and the Astrographic Catalogue. From 1905, the object-glass began to be used in eclipse expeditions and from 1922, the whole telescope. Mothballed during the Second World War, the telescope was brought back into use at Greenwich in 1947/8. It stayed at Greenwich until 1956/7 when it was moved to Herstmonceux where it was re-erected in dome D in August 1957.

 

Background to the Carte du Ciel

The Carte du Ceil has its origins in a photograph taken of the Great Comet of 1882 at the Cape Observatory, with a camera strapped onto an equatorial telescope. This was the first time a camera had been so mounted. The results were striking and attracted considerable attention, not so much for the image of the comet, but for the clarity of the surrounding field of stars. The French brothers Paul and Prosper Henry saw the potential for revolutionising the process of chart making and developed a photographic telescope with an objective of 13 inches aperture.

On the invitation of the French Academy of Sciences, an International Congress on Astronomical Photography, was held in Paris in April 1887 April. There, a scheme was approved for the photographic mapping of the heavens by the concerted action of a number of observatories in both hemispheres with a standardised telescope. According to this scheme two sets of photographs, each covering 2º by 2º (on a scale of about 1 mm to 1 minute of arc) were to be taken on 16-cm square photographic plates: one with long exposure (40 minutes) to form a photographic map of the whole sky (Astrographic Chart), and the other with short exposures (6m, 3m, and a supplementary exposure of 20s) from which a catalogue of reference stars was to be formed (the Astrographic Catalogue). Each set was to be taken in duplicate, the centres of one series being at the corners of the other. A reséau (grid) of cross-lines 5 mm apart was to be photographed on each plate to facilitate the determination of positions of stars.

The Astronomer Royal, William Christie attended the conference as delegate of the Royal Society. At the meeting of the Board of Visitors on June 8, it was recommended that provision should be made to enable the Royal Observatory at Greenwich to take part and that steps should be immediately taken to provide the Royal Observatory with a suitable instrument. The sanction of the Treasury to the necessary outlay was obtained in 1888 August, and instructions were immediately given to Sir Howard Grubb, (with whom Christie had been in previously communication) to proceed at once with its construction. The instrument was delivered to Greenwich in May 1890. It was brought into working order and subjected to testing over the following year, with the production of plates for the Carte du Ceil beginning in December 1891.

The plate carrier of the Astrographic Refractor, c.1900. Reproduced under the terms of a Creative Commons Attribution-NonCommercial (CC BY-NC) licence courtesy of whatsthatpicture (see below)

The Astrographic Refractor and the clock Dent 2017, c.1900. The clock was erected on 14 March 1891 (RGO7/29). Reproduced under the terms of a Creative Commons Attribution-NonCommercial (CC BY-NC) licence courtesy of whatsthatpicture (see below)

 

Participating Observatories

Twenty observatories from around the world participated, each of which was assigned a particular region of the sky to photograph. In total, over 22,000 (glass) photographic plates were produced in a programme that extended over several decades. The Carte du Ciel component was never completed, and for almost half a century the Astrographic Catalogue was largely ignored. It eventually came into its own following the publication of the Hipparcos Catalogue in 1997 which led to its re-examination.

 

Location of the telescope at Greenwich

At Greenwich, the telescope was housed in the 18-foot dome, which had been completed in June 1888, ostensibly to provide a permanent home for a 6-inch equatorial and photoheliograph from the Transit of Venus expedition of 1874. These were never in fact mounted and the dome stood empty until the mounting of the Astrographic Refractor in May 1890.

The Astrographic Dome (right) c.1925

The dome was erected over Bradley’s old Quadrant Room and covered with papier-mâché on angle-iron. It had a sectorial shutter coming to a point at the zenith and opening 1/6th of the circumference at the horizon. This shutter was blown off in a gale of wind on 22 December 1894 (click here for image), and the instrument was out of use until 2 February 1895 while the shutter was being repaired, more secure fastenings being provided.

The instrument was at a height of 30 feet above the ground. The pier on which it rested having been built on the top of the old Quadrant Pier, firmly connected to the walls of the building below, but carefully isolated from the upper storey and observing floor.

 

The Astrographic Catalogue (Greenwich Section)

The Greenwich Section of the Astrographic Catalgue was published in six volumes between 1904 and 1932:

Astrographic Catalogue, Vol. I (Dec. +64º to +72º)
Astrographic Catalogue, Vol. II (Dec. +72º to +90º)
Astrographic Catalogue, Vol. III (R.A., Dec. and magnitude of Reference Stars)
Astrographic Catalogue, Vol. IV – Proper Motions and Photographic Magnitudes
Astrographic Catalogue, Vol. V – Proper Motions of Stars (Dec. +64º to +72º)
Astrographic Catalogue, Vol. VI – Proper Motions of Stars (Dec. +72º to +90º)

Click here for information on the volumes published by other observatories (over 200 volumes in total).

 

Eclipse Expeditions (1905–29)

 

Year Eclipse Location Comment
1905 Aug 30 Tunis Object-glass (OG) only. 29 July 1905, left London on SS. Sumatra for Malta. 7 August, arrived Malta and transferred to the H.M.S.Suffolk. 18. 18 August, taken to Sfax, arriving 19 August. Landed and carried to observing station the same day. 30 August, re-packed. 1 September, loaded onto H.M.S.Suffolk and takento Malta where it was transferred to a lighter where it remained until 8 September when it was loaded onto the S.S.Formosa. 17 September, arrived Gravesend. 19 September 1905, unloaded and returned to Observatory. OG was mounted in a wooden tube which was able to carry a square plate measuring 10 inches by 10 inches. A mahogany block was fixed to the OG section of the tube into which a steel ring 13½ inches diameter was let. The cell of the OG was attached to this ring by three adjsting screws
1919 May 29
Brazil Object-glass only.
1922 Sep 21
Christmas Island July 1921, telescope dimounted at Greenwich for alteration and adjustment. 28 January 1922, shipped to Christmas Island with specially made stand. 21 March, arrived Christmas Island. By 1 May, mounted and adjusted. 4 December, returned to Greenwich. 31 December 1922, remounted and ready to use.
1929 May 9 Siam (Thailand) 12 Feb 1929, dispatched from Greenwich to Liverpool with stand used for the Chrismas Island eclipse. 16 Feb, shipped from Liverpool by S.S. Laomedon.

 

Howse (1975) states that the telescope was also taken the Giggleswick in Yorkshire for the eclipse on 29 June 1927. The report submitted by Dyson for publication in the Monthly Notices of the Royal Astronomical Society, Vol. 87 suggests otherwise.

 

Post war

Mothballed during the Second World War, the telescope was brought back into use at Greenwich in 1947/8 when it was employed for experimental work on photo-electric guiding for possible future use with the Transit Circle and supplying the Isaac Newton Telescope with fully automatic guiding capable of correcting atmospheric effects several times a second.

In March 1950, the instrument was restored to full working order, with the restoration of  the gravity drive, the control pendulum of the 26-inch refractor being used in place of the original pendulum which had seriously deteriorated during 11 years of forced disuse. The 3-inch finder scope was also replaced; having at some time in the past developed a crack (see the annual report for 1951 for more details).

As the only one of the large refractors to have been brought back into use, it was used for observations of comets and the brighter minor planets, occultations and the testing of a camera constructed around a 5½-inch Ross aircraft reconnaissance lens.

The telescope stayed at Greenwich until 1956/7 when it was moved to Herstmonceux and re-erected in August 1957 in Dome D where is still remains, a new mounting having been provided by Grubb Parsons in 1969. The old mounting is now in the care of the National Maritime Museum (Object ID: AST0931). In the mid 1960s, the 6-inch Franklin Adams wide-angle Star Camera was mounted piggyback onto the Astrographic Refractor. It was used during the reporting year 1965/6 to search for new variables by comparing the developed plates using a technique known as ‘blink’ comparison. Still mounted on the Astrographic Telescope in 1985, its current whereabouts is unknown.

The Astrographic Refractor at Herstmonceux in 2011. Reproduced under the terms of a Creative Commons Attribution-NonCommercial-NoDerivs (CC BY-NC-ND) licence courtesy of Melanie Davies (see below)

 

Contemporary accounts

The Astrographic Telescope and its method of use were described in some detail by Chrisitie in the introduction to the first volume of the Greenwich Section of the Astrographic Catalogue. The use to which the telescope was put each year, together with any alterations to it, were normally recorded in the annual reports.

 

Further Reading

Turner, H.H. The Great Star Map (London, 1912). Note: in this online copy, pages 156 & 157 appear at the start of the book.

Perryman, Michael. The making of History’s Greatest Star Map (Heidelberg: Springer, 2010)

Perryman, Michael. The History of Astrometry (2012)

Wayman, P. A. The Grubb Astrographic Telescopes, 1887-1896. Mapping the Sky: Past Heritage and Future Directions: Proceedings of the 133rd Symposium of the International Astronomical Union, held in Paris, France, 1-5 June 1987. Edited by Suzanne Debarbat. International Astronomical Union. Symposium no. 133, Kluwer Academic Publishers, Dordrecht, p.139

 

Image Credits and licensing arrangements



Second from top (left) The plate carrier of the Astrographic Refractor, c.1900. Reproduced under the terms of a Creative Commons Attribution-NonCommercial (CC BY-NC) licence courtesy of whatsthatpicture. For link to original image click here
Second from top (right)
The Astrographic Refractor and the clock Dent 2017, c.1900. Reproduced under the terms of a Creative Commons Attribution-NonCommercial (CC BY-NC) licence courtesy of whatsthatpicture. For link to original image click here


Bottom The Astrographic Refractor at Herstmonceux in 2011. Reproduced under the terms of a Creative Commons Attribution-NonCommercial-NoDerivs (CC BY-NC-ND) licence courtesy of Melanie Davies. For link to original image click here