Reflecting the heavens

In the past I have written about the problems of deciding who actually invented the reflecting telescope and also about John Hadley the man who, about fifty years after Newton had made the first functioning reflecting telescope, finally succeeded in manufacturing them. Today I want to look at the greatest maker of reflecting telescopes in the eighteenth century, James Short who was born on 21 June 1710 (NS).

James Short

The orphaned son of a wright Short was destined for the Manse when he entered Edinburgh University in 1726 to study classics and divinity but fate in the form of mathematics professor Colin MacLaurin had another future in store for him. Inspired by MacLaurin’s lectures Short abandoned divinity for mathematics and astronomy. Recognising the young man’s talents MacLaurin allowed him to use his own rooms at the university as a workshop. Short began experimenting with the construction of reflecting telescopes in 1732.

After initial failures to construct mirrors of silvered glass Short perfected Newton’s metal mirror alloy, speculum, and began producing parabolic telescope mirrors. Whereas Hadley had gone for the relatively simply Newtonian telescope design with a parabolic main mirror and a plain secondary mirror

 A Newtonian Telescope

Short started making the much more complex telescopes according to the design of fellow Scotsman, James Gregory, with a parabolic main mirror and an ellipsoidal secondary mirror.

A Gregorian Telescope

Short perfected the art of grinding and polishing these difficult shapes and as this knowledge provided the source of his not inconsiderable success as a telescope maker he never revealed how he was able to do so. By 1734 he was manufacturing telescopes in several different sizes and according to MacLaurin they were far superior to those of his rivals. In 1735 MacLaurin informed the Royal Society in London of his achievements who then tested some of Short’s telescopes in 1736. In the same year Short was engage by the Queen to instruct her younger son William, Duke of Cumberland in mathematics. Shorts royal pupil would go on to become notorious as “Butcher Cumberland” following the Battle of Culloden. In 1737 Short was elected as a fellow of the Royal Society. Also in 1737 Short became a founding member along with MacLaurin of the Philosophical Society of Edinburgh. Short had manufactured 180 telescopes in Scotland before he left to set up shop in London in April 1738. He left Scotland already established as a leading instrument maker and as a wealthy man.

A Short Reflector

Short quickly became established in London, then the leading European centre for the manufacture of scientific instruments, or as they were known then, philosophical instruments. Short was on friendly terms with all of the leading London instrument makers but in one thing he differed strongly from all his friends and competitors. Whereas Shorts friends all had specialities, John Bird for example was famous for his wall quadrants, George Graham for his clocks and John Dollond for his refracting telescopes, all of them ran large workshops in which they and their employees produced a wide range of instruments of many types; Short however only produced reflecting telescopes and with few exceptions they were all Gregorians. Short was a specialist and although his instruments were on average twice as expensive as those of his rivals he became the leading European maker of reflecting telescopes. His largest, and most expensive, instrument was an eighteen-inch aperture reflector for the King of Spain, which cost £1200. To put this into perspective an assistant astronomer at the Royal Observatory in Greenwich earned £30 p.a. at this time. Short also constructed a large reflector for the observatory in Uppsala, which brought him the rare distinction of a foreign membership of the Swedish Royal Academy of Science in 1758. Despite his financial success Short obviously valued such honours and titles because he applied for and received an MA degree from the University of St. Andrews in 1753.

Short was not just a maker of telescopes but also a respected astronomer who regularly published reports of his observations in the Philosophical Transactions of the Royal Society. He also calculated the size of the astronomical unit based on the results of many of the observations of the transit of Venus of 1761, many of these observations being made with Short’s own instruments. These calculations led to a bitter dispute with the French astronomer Alexandre Guy Pingé (1711 – 1796) whose results differed substantially from those calculated by Short. Short accused Pingré of having messed up his observations and Pingré countered by accusing Short of having screwed up his calculations. The dispute rumbled on in varies journals and pamphlets until Short’s death in 1768. In the end history would prove Short half right. Pingré’s observations had been good but his determination of the longitude of his observation position was wrong. Short was also heavily involved in the preparations for the 1769 Venus transit supplying telescopes for many of the European expeditions, including the instruments used by Green and Cook on Tahiti but did not live to witness the event himself.

Short was also involved in the British efforts to determine longitude at sea serving on the parliamentary committee to organise the sea trials of John Harrison’s H4 conducted by Charles Green and Nevil Maskelyne in 1763. Short was a close fried of Harrison’s a friendship that supposedly cost him the job of Astronomer Royal. Harrison appears to have suffered from some form of dyslexia or dysgraphia and had great difficulties formulating written applications for grants etc. Short is known to have helped him write his petitions to the Board of Longitude. In 1763 an anonymous printed pamphlet appeared in London praising Harrison’s achievements and criticising his treatment by the Board. Rumour had it that Short was the author of the pamphlet, a rumour that purportedly led Short’s patron Lord Morton, then President of the Royal Society, to oppose Short’s candidature for the position at Greenwich in 1764, although he acknowledge his superior qualifications for the job. Short’s criticisms of the quality of the Greenwich observations also probably played a role in the story.

Short’s restriction of his workshop to only making Gregorian telescopes was not his only unusual practice as an instrument maker. Usually the instrument makers made all of the parts for their instruments, lenses or mirrors, cases, and stands in the case of telescopes, in their own workshops; Short did not. Short only made the mirrors for his telescopes himself, farming the rest of the work out to other craftsmen and then assembling the finished product before selling it to the customer. His workshop practices were also fairly revolutionary. He is thought to be one of the first telescope mirror makers to use optical methods to control the grinding and polishing of his mirror. Using beams of light reflected from the surface being worked to control the curvature. He also produced his mirrors in batches and then paired main and secondary mirrors out of the batches to find the best combinations turning the mirrors as well around their central axis to find the best positions for optimal magnification. Once this had been determined he marked the mirrors so that it was possible to dissemble and reassemble the telescope without loss of quality. This careful personal attention to detail was the key to Short’s immense commercial success.

Having outlined Short’s working methods I would like to correct an error in Jenny Uglow’s excellent Lunar Men:The Friends Who Made the Future. In 1755 the nineteen year old James Watt, he of steam engine fame, travelled down from Scotland to London to learn the trade of philosophical instrument maker. He carried with him a letter of recommendation to James Short written by Dr Robert Dick, professor of natural philosophy at Glasgow College. Uglow claims that Short refused to help Watt and turned him away. This is not true. With his very narrow specialisation Short could not offer Watt the type of general apprenticeship that he was looking for. He did however pass him on to another philosophical instrument maker, John Morgan, who could and did give Watt what he was looking for.

Short was in the habit of carefully numbering the instruments that he made so we know that he manufactured at least 1370 telescopes before he died leaving a fortune of £20 000. One great irony of Short’s highly successful career is that although he made so many high quality telescopes that travelled all over the world and of which many still exist today, no major astronomical discoveries were made with a Short.

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Filed under History of Astronomy, History of Optics, History of science

6 responses to “Reflecting the heavens

  1. Pingback: Reflecting the heavens | Whewell's Ghost

  2. Gordon

    So Green & Cook(e) used a Gregorian reflector for their Venus transit observations.

    • Yes, both Green & Cook used Gregorian reflectors built by James Short for their Venus Transit observations. Not one but two as they observed separately.

      • Thanks Thony. I guessed there were 2 Gregorian telescopes from your article.

        Interesting that one doesn’t see many Gregorian telescopes around these days, especially amongst the amateur groups and the commercial interests supplying the amateurs. Not sure why that is. Perhaps too complicated to make?

      • Newton’s are simpler and therefore cheaper to make and for most amateur astronomers adequate for their purposes. For professionals and for amateurs who want a high performance telescope the Cassegrain, which is superior, has largely replaced the Gregorian.

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