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| On this trade card, c.1828-9, the English spectacle maker William Dowling chooses the image of Sacharias Jansen to add prestige to his business. Dutch writing from the mid 17th c. indicates that Jansen may possibly have invented a telescope as early as 1604. A travelling merchant as well as an optician, Jansen was a bit of a rogue, involved as he was in counterfeiting copper coins, so perhaps he was not a good example for Dowling to choose! |
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| A Dutch telescope with rayskin-covered barrel from the turn of the 17th and 18th centuries. |
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| Euler (1707-1783) was a Professor of Mathematics. The engraving by Holl is of a picture by A. Lognac (?) in the collection of the Institute of Ophthalmologists. In 1747 Euler suggested using a combination of flint and crown glass coupled together to combat chromatic aberration - a solution not put into practical production until the 1750s which had, however, been understood by Chester Moor Hall since the period 1729-33. |
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| John Dollond I, holding a lens and touching Newton's book on Opticks. |
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| Mortar allegedly used by John Dollond to grind flint for the first achromatic lens, 175 |
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| Portrait of Peter Dollond by Hoppner, before 1800 |
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| A telescope of uncertain date, featuring decorative Mother-of-Pearl panels on the barrel and a shutter to cover the objective lens |
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Dr William Kitchiner (1775-1827), holding a terrestrial telescope. An engraving by Thomas Woolnoth after the painting by Joseph William Rubidge. Also a detail showing a refractor from the Encyclopedia Londoniensis |
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| Telescope by Watkins & Hill of Charing Cross, c.1820-1850 |
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A typical mid-19th century Dollond of brass with a leather-covered barrel |
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Lithograph after a drawing by Paul Gavarni of a Parisian street stall selling telescopes, 1829 |
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A 19th c. French ivory and brass pocket telescope, unsigned, with a cardboard case and an auxiliary tinted lens cap |
This page concentrates on the telescopes, for siderial or terrestrial use, in our own collection or those illustrated in our pictorial collections. It also pays special regard to Dollond telescopes which were amongst the most popular in both Great Britain and abroad for a period of over one and half centuries.
In the beginning
The invention of the hand-held telescope is generally ascribed to the Dutch spectacle maker Hans Lipperhey of Middelburg who in 1608 discovered that holding a convex and a concave lens apart from each other, then looking through the two together, could produce a 'far-seeing' effect. Not all historians agree and some have advanced the claims of Lipperhey's neighbour and rival, Sacharias Jansen, or Jacob Metius to have been the inventor. We could even be considering the wrong century since there is circumstantial evidence for an earlier refracting telescope designed by the English mathematician Leonard Digges and made by his son Thomas in the second half of the sixteenth century. This story is not generally, however, given much weight. The more unreliable websites often cite Galileo as the inventor of the telescope. This is ridiculous. We know that he heard of Lipperhey's work in the Netherlands and this prompted him to begin his experiments. Galileo is correctly credited with having been the first to make extensive use of the refracting telescope for astronomical observations.
Lipperhey was actually born in Germany but moved to Middelburg in the Spanish Netherlands in 1594. In a famous incident of 1608 he arranged a demonstration of his new device to the authorities, with the intention of taking out a patent. Lipperhey is the man described as a Un faiseur de lunettes de Mildebourg, pauvre homme, fort religieux & craignant Dieu (a spectacle maker from Middelburg, a humble man, very religious & pious) at the end of a report from a Siamese emissary. From the Maurits Tower in Den Haag they saw the clock of Delft and the windows of the church in Leiden, 'and even the stars'. As this was a time of truce, Spinola the commander of the Spanish army was present at the demonstration, a fact which may otherwise have raised eyebrows. Notwithstanding the mention of stars, which suggests that astronomical observation was a use for the telescope from the very outset, it was mainly conceived as having a military application.
In August 1609 Della Porta produced the first sketch of a telescope in a letter. We do not have any images of Lipperhey's instrument; indeed the first Dutch illustrations of telescopes do not occur until 1623-4. They were produced by Van de Venne who also happens to have lived in the same street as Lipperhey.
In 1610 Snellius wrote about a very small telescope in a letter to a friend. This is another very important early reference.
Did you know?
The spelling of Lipperhey's name is often given incorrectly in the English literature as 'Lippershey' (with an 's'). The origin of this mistake has been traced back to a slip of the pen by Gerrit Moll, director of the Observatory at Utrecht, in a publication of his, dated 1831.
Refracting Telescopes
The Galilean telescope intercepted the convergent light rays from the objective end of the instrument before their arrival at the focal surface by means of a concave lens acting as an eyepiece, thereby forming an erect but virtual magnified image. Galilean refractors were relatively small in size. A typical objective lens for a later telescope of the same type might measure two inches. Although still in use today, in seaside viewing scopes, this inferior design was soon modified by the German astronomer and mathematician Johannes Kepler, who in 1611 replaced the concave lens of the eyepiece with a convex lens relocated behind the focal surface to form an inverted but real image, thereby also establishing the basic design of all subsequent eyepieces. Kepler's device offered more magnification and a wider field of view (useful when scanning the night sky for hard-to-spot celestial objects). Its upside-down image did not matter so much for astronomical observations, but the Keplerian telescope suffered from even worse chromatic aberration.
See elsewhere on this website for more on Kepler and astronomical optics.
It is a point not commonly appreciated that, after a burst of inventiveness from 1608-11, all possible discoveries relating to the design of telescopes were over by 1612 and telescopes thereafter were at best a curiosity for at least the remainder of the first half of the seventeenth century. The maximum magnification of which they were capable settled at about X30. Very large telescopes are a feature of the second half of the seventeenth century, when they could become very long indeed.
Reflecting Telescopes
Not all telescopes relied solely lenses. Some used metal mirrors to reflect the light from the objective end of the telescope to the observer's eye. The Scottish mathematician James Gregory published a design for a reflecting telescope in 1663, but the first usable instrument was built to a different design by Isaac Newton in or around 1670, apparently with knowledge of Gregory’s design. The Gregorian telescope proposed a concave primary mirror perforated by a central hole opposing a smaller concave secondary mirror located outside the focal point of the primary, such that light reflected from the primary would be captured by the secondary and reflected back through the hole in the primary to a focal surface. Newton modified this difficult-to-construct design by replacing the concave secondary with a flat mirror angled at 45 degrees to the optical axis of the primary mirror and by doing away with the central hole in the primary, such that light reflected from the primary would be intercepted by the secondary before coming to a focus, and directed at 90 degrees to a focal surface located out of the path of the incoming light. At about the same time as Newton and Gregory, and apparently working completely independently, a French priest Laurent Cassegrain is now believed to have been the inventor of a third basic design of reflecting telescope (the Cassegrain) similar to Gregory’s, but in which the secondary mirror is convex rather than concave and is instead located inside the focal point of the primary mirror. Although theoretically superior to both Gregorian and Newtonian designs due to the tendency of any error in the concave primary to be cancelled out by the convex secondary, the Cassegrain design did not become widespread until the late nineteenth century, because of the additional difficulty of making a convex mirror. In all designs, mirrors were made of an alloy of tin and copper with a small admixture of arsenic, also invented by Newton and called speculum metal. Although very brittle and hard to cast, a successful casting produces a highly reflective surface when polished.
The problem with reflectors was that the mirrors tended to oxidise very fast, at which point the telescope would become 'blind'. They were also difficult to manufacture since you couldn't really control the shape of the mirror during the production process. Reflectors do not distort the image they produce if you have a perfectly shaped mirror, but the difficulty of obtaining that perfection deterred many makers. Newton only ever made two.
Achromatic Refracting Telescopes
As Newton had observed, early optical devices suffered from colours at the edges of the image - 'chromatic aberration'. The dispersion of the light rays depends upon the quality of the refracting surface. Chester Moor Hall, a barrister who practised optical experiments as a hobby, worked to counter these 'deletrious chromatic fringes' and eventually solved it by commissioning a lens of two separate parts, made from different materials (one half concave flint glass, the other half convex crown glass) and with opposite powers. These cancelled each other out and produced an image which, whilst not perfect, went a good way towards the goal of interference-free optics.
In a fateful decision Hall commissioned one half from Edward Scarlett and one half from James Mann, but both opticians sub-contracted the project to the same lens grinder, George Bass. In 1747 John Dollond, then still an amateur optician, wrote to the eminent (and blind) Swiss mathematician, Leonhard Euler criticising his attempt to suggest that correcting spherical and chromatic aberration in object-glasses was possible. In the 1750s, by now a professional instrument maker, he began experimenting with objective lenses based on his interpretation of Newtons's Opticks. Early efforts resulted in telescopes with multiple eyepiece lenses. Four of five of these lenses could combine to enhance the performance of a refracting telescope considerably. Refractors had to be very long, however, in order to accommodate the focal length dictated by the small aperture. Larger apertures would have resulted in too much aberration and a very indistinct image.
In 1757 John Dollond visited the workshop of George Bass, the lens grinder and polisher where he seems to have accidentally noticed the lenses of Mr Hall and discovered that flint glass held the solution. He conducted various trials with English crown glass, 'Venice' glass and English flint glass (white crystal), establishing that the last type had the most divergent properties. These experiments were written up by James Short through whom they were conveyed to the Royal Society. Peter Dollond perusaded his father to seek to protect the discovery by means of a patent application. This was granted in 1758 and shortly afterwards the Royal Society awarded John Dollond its highest decoration - the Copley Medal.
- An achromatic telescope 3 feet in length could now produce the same quality image as a non-achromatic telescope of 45 feet.
After John Dollond's death in 1761 the patent was frequently infringed. Contemporary trade literature shows that opticians such as Benjamin Martin or George Adams stocked both achromatic and 'ordinary' telescopes. Dollond's rivals felt justified in this as the story of Chester Moor Hall's earlier work became more widely known. In 1764 some 35 spectacle makers petitioned the crown to annul the patent and curiously the Worshipful Company of Spectacle Makers supported the petition against one of its own most eminent members. Emerging victorious from the case, Peter Dollond embarked upon a series of selective lawsuits against his principal opponents including James Champneys, Addison Smith and Francis Watkins. Through fierce protection of his patent rights Peter Dollond grew increasingly prosperous. The business relocated to St Paul's Churchyard in 1766. He developed the triple-lens achromatic telescope which resulted in an even finer image. The patent finally lapsed in 1772.
Dollonds
For a time in the eighteenth and nineteenth century the word 'Dollond' was almost a generic term for telescope rather like 'Hoover; is to vacuum cleaner. Genuine Dollond telescopes were considered to be amongst the best.
Peter Dollond (1731-1820) was the business brain behind the company which he founded in Vine Street, Spitalfields in 1750. The Dollonds were originally Huguenot refugees in the silk weaving trade so characteristic of that part of London. In 1752 he entered into a business partnership with his father John (1706-1761) and the shop was relocated to a position under the sign of the Golden Spectacles and Sea Quadrant in Exeter Exchange, off The Strand.
The Dollonds seem to have made both types of telescopes (reflecting and refracting), possessing the technology to produce significant numbers of lenses free of chromatic aberration for refracting telescopes by 1758, after which reflecting telescopes became less popular. Gregorian types of reflector are common enough, the rare examples being those that were not designed to be used with a stand. The dating of such items is often based mainly on the case (skin replacing leather in the mid 18th c.), where one exists.
- 1764 - Leopold Mozart (father of Wolfgang) bought a Dollond 3-foot achromatic telescope with double objective lens.
- 1766 - Frederick the Great instructed his London ambassador to buy two telescopes from Dollond's 'because they magnify extraordinarily the object'.
- 1769 - A Dollond telescope sailed with Captain Cook in 1769 on his voyage to observe the Transit of Venus.
- 1780 - Dollond introduced the Army Telescope (or 'Improved achromatic telescope') . This is the standard type so often found by modern collectors with a mahogany body and brass draw-tubes. They were between 14 and 52 inches long with a lens aperture of between 1 and 2.75 inches. They cost from 2.5 to 12 guineas.
- 1786 - Thomas Jefferson visited P+J Dollond and bought a telescope for 10 guineas.
- Admiral Lord Nelson made a special visit to purchase a Dollond.
Because Dollond & Co's records were destroyed by fire it is not usually possible to trace the lineage of individual telescopes even when the serial number is present.
It might seem churlish to mention it, but 'Dollond' is actually spelt with an 'o' as the fifth letter. Many people get this wrong. If a telescope is marked 'Dolland' (with an ‘a’) then it is quite likely a counterfeit product. It may well be 19th c and a good example in its own right, but at the time it would have been considered inferior to the genuine branded article. Many manufacturers, some small and some not so small, sought to cash in on the Dollond name (with a letter 'o') - and marked their wares accordingly.
The advantage of reflectors was that they could be considerably shorter in length than the terrestrial refractor. Even after Dollond had solved the problem of chromatic aberration the company faced a constant struggle to obtain sufficient amounts of quality glass, resulting in the manufacture of telescopes with smaller objective lenses than might have been desired. In some surviving examples the eyepiece end has a wider diameter!
Peter Dollond often corresponded with Dr William Kitchiner. As well as a gourmet cook, Kitchiner was a lecturer on optics and author of 'The Economy of the Eyes' (1824) and 'Spectacles, Opera Glasses and Theatres' (1826). His memorial stone, recording his work on telescopes, may be viewed inside St Pancras Church in London. Kitchiner described Peter Dollond as 'The Father of Practical Optics'. In tests he conducted on ten telescopes the one made by Dollond allowed him to observe details which its rivals 'were not perfect enough to define at all'. Kitchiner collected over fifty telescopes in all and was not afraid to pass judgment. He once stated: 'Beyond a certain size, telescopes are only just as useful as the enormous spectacles which are suspended over the doors of opticians'.
Dollond & Co merged with Aitchison & Co in 1927 to form Dollond & Aitchison, the well-known high street chain of opticians. They no longer manufacture but are exclusively a retail operation. The Company does not possess historic records of its former products and enquiries made directly to the company will normally be redirected to us here at the BOA Museum. For more information on the company itself see the book by Hugh Barty-King, 1986, Eyes Right: The Story of Dollond & Aitchison, 1750-1985 (Quiller Press, London). A copy can be studied in the BOA Library.
If your interest is in the smallest type of telescope, you may also enjoy our webpage about spyglasses.