Historical Astronomical Heliostat Norman Lockyer c.1870
This is an astronomical heliostat, using the geometry of the Silbermann heliostat. (For more details of this geometry see the Silbermann Heliostat on this web site).
It was made by John Browning, 63 The Strand, London, who moved to this address some time between 1868 and 1872. The compass is signed Spencer & Co. 111 Minories, London. The firm was at this address from 1840-1870.
This heliostat was made for a telescope with an external diameter of the objective housing of 6.5" diameter mounted horizontally at the end opposite the mirror mounting. There is an adjustable wood "V" shape at the rear of the round sleeve to support the telescope body, so that the weight of the front of the telescope is not wholly borne by the objective lens mounting.
First question: What was this instrument used for?
Heliostats in general are not sufficiently rigid and accurate for astronomical work generally "their only serious application to astronomy being in the early days of solar spectroscopy." (ref: Lockyer, J. N. The Chemistry of the Sun. quote Mills, A.A. Heliostats, Siderostats and Coelostats. Journal of the British Astronomical Association, 95 (1985), 89-99).
As this instrument can be dated to just pre or circa 1870, it is certain that researching the solar spectrum was exactly what this instrument was designed to do and this fits precisely with the dates when this research was being carried out in England and France.
Second question: Who was it made for?
All the Victorian heliostats, of which I am aware, were made on the continent, this example is the only British (Victorian) model that I have seen and as it was found in the England it seems a pretty certain bet that it was made for a British scientist. Like all larger astronomical instruments this was made for a specific telescope, so how many British scientists/astronomers were studying the solar spectrum in the period circa 1865 - 1875?
There would appear to be just three 'amateur astronomers' at this period doing serious solar spectrum research in England: William Huggins, the Jesuit monks at Stoneyhurst College and Norman Lockyer. The large national observatories were concerned with mapping the skies at this time; they didn't carry out spectral research.
William Huggins used an 8" telescope for his researches so this heliostat wasn't made for him. The monks at Stonyhurst College used an even larger instrument.
Joseph Norman Lockyer was born on May 17th 1836. In 1861. He bought his first telescope, a refractor made by Thomas Cooke (thought to be 3.75" diameter). Cooke encouraged Lockyer's interest in astronomy and in 1862 lent him a 6.25" object glass to build a telescope with which he was to make his important observations during the next ten years. If one mounts a 6.25" objective lens the external diameter of the mounted lens would be 6.5" which is an exact fit for this heliostat. Unless another astromomer can be found doing solar spectrum research with a 6.25" telescope at this period (and the chances of that would appear extremely remote to put it mildly), this heliostat can only have been made for Norman Lockyer.
In 1868 Norman Lockyer discovered helium in the solar spectrum nearly three decades before it was isolated on Earth.
Lower arm on mirror mounting replaced.
Front Silvered Mirror 10.1" (25.5 cm) x 6.5" (16.5 cm) Wood base board 35.5" (90 cm) x 9.5" (24.5 cm) height 20" (51 cm). Transport at cost.
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