Orwell Astronomical Society (Ipswich)

George Calver (1834-1927)

Several revered astronomers of old were associated with East Anglia. One such, a native of the region, was George Calver (1834-1927), who truly was Master Mirror Maker of the late Victorian and Edwardian era. A Suffolk man, he was born at Walpole near Halesworth in July 1834, the son of farm labourers who died when he was very young. (Census records at various dates provide inconsistent information on his place of birth, locating it as far apart as Ipswich and Great Yarmouth!) By the 1850s he was apprenticed to a local shoemaker, eventually moving on and setting himself up in business at Great Yarmouth where he met his wife to be, Hannah.

Calver's latent astronomical interest was fired by his local non-conformist clergyman, the Rev Matthews, who showed him the splendours of the night sky through his excellent reflecting telescope, the mirror of which had been ground by the leading maker of the day, G H With of Hereford. With, a Professor of Science, was a pioneer in the manufacture of silver-on-glass mirrors, which were rapidly gaining popularity over speculum mirrors (made from a mix of copper and tin). Calver was deeply impressed with the optical performance of Matthews' instrument and when challenged by Matthews to try to produce a mirror of equal or better quality he embarked upon what proved to be a lifetime's work. That very challenge would seem to indicate that Calver was already dabbling in mirror making. He began a regular correspondence in a leading scientific magazine of the day, The English Mechanic; his many letters at first sought to question other correspondents on their mirror making techniques but at length his own experience began to show through and his later letters were full of experience and advice for the benefit of others. Perhaps his best move was to write to With directly for information on his methods. A frequent exchange of letters began between the two who, one may argue, were rivals¹ in the supply of mirrors - but always on the most cordial of terms and always ready to share ideas. At the outset, With sent Calver a comprehensive account of his production methods, informing him that he polished his mirrors on a device which he described as a simple form of Lord Rosse's machine, with stroke and slide motion².

One of Calver's first telescopes was a 10" Newtonian made for his own use and with which he became a proficient observer of Jupiter and double stars. By 1871 his mirrors were beginning to be noticed by the market of the day and he moved to new premises at Widford, just outside Chelmsford. His business began to grow and he took on a small staff to cope with the lengthy order book. He used machinery for grinding and polishing but always completed the figuring work with his own hand. He performed workshop testing by pinhole, knife edge and eyepiece methods. He also used a highly polished black glass ball placed 100-500 yards distant to pick up an image of the Sun to provide an artificial star, a method developed by With. But Calver insisted on final tests being made on "nightime" stars, using high powered eyepieces. Most of his mirrors were slightly under-corrected to allow for the effect of night-time cooling. Calver constructed telescope mounts to his own designs, subcontracting some of the work to a firm with whom he became familiar during his time at Great Yarmouth, Messrs T Lepard & Sons.

Calver's mirrors were priced at the higher end of the market and their quality made them a "must have" for a very great number of astronomers, both amateur and professional, in the UK, throughout the colonies and beyond. His business expanded, bringing financial rewards, and he and Hannah were able to move upmarket from their modest home, Little Hylands in Widford Street to Hill House in Widford End. They were sufficiently well heeled to engage a servant, a young girl from Hannah's native Great Yarmouth.

Most of Calver's mirrors were in the range 5" to 8", f/9 to f/12, in both Newtonian and Cassegrain configurations on the sturdiest of mounts. He also made larger mirrors to order from 10", 12", 15", 18" up to 37". One of the latter is in use to this day on the Crossley Reflector (1895) at the Lick Observatory.

However, it wasn't all success and, in 1884, one of Calver's manufacturing efforts failed spectacularly when he was commissioned by Sir Henry Bessemer (of Bessemer Furnace fame) to make a 50" mirror. Bessemer had conceived the idea of a cut-price large mirror by applying suction to a thin glass spherical mirror and polishing it over a "pressure cup". The mirror was never mounted in a telescope and its eventual fate is unclear, although there is a school of thought that it was cut up into several smaller mirrors. The failure did not dent Calver's confidence and, some time later, when Mr James Lick offered a prize for a world record sized mirror, Calver caused a sensation in the telescope-building world by offering to produce a mirror of 100" diameter. His offer was never taken up! Bear in mind that this was some considerable time before G W Richley and his team finally produced a 100" mirror in 1917 for the giant reflector at Mount Wilson Observatory, California, after six years of figuring work.

In 1884, one of Calver's 10" reflectors won a bronze medal when exhibited at an international science exhibition at Crystal Palace. It was about this time too that he published a widely applauded catalogue, Hints on Silvered Glass Reflecting Telescopes, in the form of a thin book, illustrating his products and replete with glowing testimonials from many of the leading amateur astronomers of the day.

The coming of the railway, coupled with increasing urbanisation and dust from Chelmsford's roads (Widford stands on the former track of the A12 trunk road) forced Calver to cease telescope production there in 1904 and return to the rural tranquillity of his native Walpole. He purchased a large house (The Manse) in the village and carried on producing mirrors, working from a wooden outbuilding on the property, building telescopes and re-silvering existing mirrors, although on a much reduced scale, with just one assistant.

Calver continued working into his nineties. He died on 04 July 1927 and Hannah passed away just a year later. In his long lifetime, he is thought to have produced around 4,000 mirrors, many of which have stood the test of time and are still in use to this day. As late as the 1950s, Horace Dall³ visited The Manse and found Calver's workshop, by then a private garage, still in existence and with many detailed scribblings and optics calculations still adorning the walls along with a number of unused mirrors scattered about. George and Hannah are buried in the local churchyard. The gravestone bears the words Kind to the poor and little children but makes no mention of his lifetime work. However, his name will always be remembered in the field of optical excellence.

Footnotes

Ken Goward, FRAS

Original: Newsletter May 1999
Updated: 23 March 2023