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History of English silvered-glass reflecting telescopes

The Equatorial Reflecting Telescopes of Browning, Horne & Thornthwaite, Calver & Irving.

Concise historical notes concerning the English commercial manufacturers of silvered-glass reflecting observatory equatorials between 1861 & 1941.

The popularity of the Newtonian reflector as the instrument of choice for the amateur astronomer followed the pioneering work of George Henry With (1827-1904). He began making silvered-glass mirrors in the early 1860's following his retirement as schoolmaster at the Blue Coat School, Hereford. With did not actually make telescopes. His principal customer was John Browning (1835-1925), the London instrument maker well-known for his spectroscopes and telescopes. Browning's business flourished to c1905, possibly first starting at 1 Norfolk Street, Strand c1866. The firm had their 'factory' in Vine Street EC3 (1872-76) and Southampton Street north off the Strand (1877-82) and William Street (1887). The shop was at 111 Minories (near Tower Hill) working under the name Spencer, Browning and Co. However during the early 1870's Browning moved to larger premises at 63 The Strand. John Browning's home was in Sevenoaks, Kent, but he retired to Chiselhurst.

BROWNING #1BROWNING #2

In 1867 Browning issued a trade publication entitled, 'A Plea for Reflectors' which ran to six editions by 1876. In it he describes his range of reflecting telescopes, how to obtain the best from them, and cites numerous favourable comparisons to achromatic refractors of similar aperture. The back of the booklet contains testimonials from satisfied customers, many of them distinguished amateurs and professionals.

Browning had two commercial rivals in the field of large silvered-glass reflecting telescopes, principally George Calver (1834-1927). Calver, born in Walpole near Yarmouth, was the son of a farm labourer. His first mirror was a 10-inch f/9 made in 1862. He transferred his business to Widford near Chelmsford in 1870 to get away from the noise and vibration of traffic that made it difficult to perform the delicate figuring and testing process. However, the Widford workshop was on a dusty main road, and he eventually moved back to his old village of Walpole in 1904.

Calver followed Browning's example and issued a congruent trade publication, 'Hints on Silvered-Glass Reflecting Telescopes' which ran to six editions by 1897.

CALVER #1 c1877CALVER #2 c1877

Calver's telescopes and mountings are broadly similar in design and construction to Browning's, but evolved into a somewhat sleeker and more elegant form by the early 1880's. The castings were made by a small firm, T. Lepard and Sons of Yarmouth, and the larger castings by the agricultural firm, Suffolk Iron Foundry near Stowmarket.

CALVER #1 c1884CALVER #2 c1884

Those surviving examples of With's work demonstrate he took pride in his mirror making. He would take great pains in preparing the plate glass blanks, polishing the sides and grinding both front and back flat before commencing rough grinding. He usually signed the back face, occasionally referriing to the quality, and almost always adding a religous inscription. For example, in the case of the 9 1/8 -inch f/8 mirror depicted, which was made for George Evershed, the engraving reads, " Lord Deo" & "Doxa en Upsisthois Theo", which in translation reads, "Glory be to God in the Highest."

With Mirror c1878


In 1887 With offered for sale his remaining stock of over one hundred 'choicest reserves'. Calver purchased about sixty. Browning ceased offering silvered-glass reflectors shortly thereafter. Over a period of thirty years With produced about two hundred mirrors; considerably less than Calver. Calver was a professional telescope maker who employed several assistants, including between 1894 and his death in 1927, a factotum called Finch, who oversaw the heavy engineering, leaving Calver free to contrentrate on the optics. The estimated production of mirrors, made or refigured by Calver is an astonishing total of over 4000!

 

12-inch f/8 CALVER c1910



Browning had one other commercial competitor. The London instrument maker to the Admiralty, Horne & Thornthwaite, at 416 Strand (1876-1913). This firm offered an almost identical range of telescopes and mountings, described in their reference handbook, 'Hints on Reflecting & Refracting Telescopes' which, by 1895, also ran to six editions.

Horne & Thornthwaite #1Horne & Thornthwaite #2



Horne & Thornthwaite offered one eccentric style of mounting that Browning & Calver did not - the 'Equestrian' mounting, designed by the Rev. E.L. Berthon (1813-1899).

Berthon Equestrian

The traditional design established by Calver and continued into the first quarter of the C20th was complimented by the telescopes made by Horace N. Irving (1877-1942). Horace Irving was born in Mortlake and prior to the Boer War was employed as a plant engineer, responsible for maintaining the generator sets used at the time to supply electricity in large country houses. In 1905 he began making his own silvered-glass mirrors and telescopes and mountings. In 1915 he moved to Roehampton, and in 1918 to Cambridge House, Teddington. After a short interegnum between 1925 & 1927 when he transferred his business to Hitcham in Suffolk, he returned to Teddington before finally moving to 258 Kingston Road in 1930, where the business continued until August 2005. Horace Irving used the services of three different foundries; Tough Bros. and Moyles, both open caste iron founders at Pier Lane, Hampton Wick, and Bullen's for the non-ferrous castings. Horace Irving died on Dec. 7th. 1942, leaving the business to his youngest son, Ronald N. Irving (1915 - 2005). Although by no means as prodigious a telescope maker as Calver, Horace Irving made several hundred mirrors, and there are numerous Horace Irving telescopes and mountings still surviving, of comparable quality and robustness.

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H.N. Irving & Son 6-inch f/10 Newtonian c1935

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