A Lincoln, with a triplet for the objective

This is a medium sized telescope, a three draw with a mahogany barrel, made by Lincoln, which is typically in the late 1700s. It was probably built for a Cavalry officer, or for a country gentleman’s use. It is 7.75” (19.7cm) closed, and 22.5” (57cm) long when fully open. Outer diameter is 1.625” (43mm). Performing fairly poorly, and with lenses rattling, when it was delivered to me in 2014, the operation of the scope was much improved by getting everything back into the right place!

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The Lincoln name

The name engraved on the first draw of this telescope is quite simple: it just says Lincoln, London, with the first word in script, like a logo: and the latter word is written as “London” is typed here. So there is very little to go on to help date it. However it uses a triple lens as the objective, which would have been one of the ways to avoid infringing the Dollond Patent, which maybe lasted from 1762 through to around 1785, although he did petition to extend the life of the patent….. I must check that out. A similar triple lens would not have been used before 1762, so it was not made by Thomas Lincoln, who was active from 1720-1762, but by his son, Charles Lincoln, who operated 1765-1805.

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The picture above shows the name engraved on the first draw, but it is significant that it is what I would describe as on the ‘right hand side’ of the telescope. This means the first letters of the lines, the “L” of Lincoln and London, are closest to the eyepiece. This is the old fashioned style, dating from early C18th up to about 1790. After that, the fashion changed, and the end of the word was closest to the eyepiece. However, it is always possible that Lincoln clung onto this approach, and continued writing his name the way he always had done! So it is generally an indicator of earlier than 1790, but this varies from maker to maker.

The three draw design, which requires three separate different sized tubes, was probably not possible before 1760 either. It is a design that maybe appeared in the 1770s-1780s. After Thomas Lincoln died, in 1762, his son Charles took over the business, and is recorded as an Optical Instrument Maker operating from 1765 to 1805. This telescope could be from anywhere within the 1780-1805 period.

Charles Lincoln operated from Leadenhall Street in London, a popular area for optical instrument makers. From 1772 onwards he was at 62 Leadenhall Street, with an address starting with “Sir Isaac Newton’s Head” – presumably this was the sign over the door. One of his apprentices was a William Cox, who later traded in London, but this Cox was not related to the Plymouth/Devonport-based William Charles Cox.

Telescope design

As mentioned above, the triple objective lens is distinctive, as it is made from two crown glass convex lenses (with a greenish tint) and one concave flint glass lens (clear of colour). These lenses are not well held within the brass ring at the end of the barrel: it appears that the ‘as made’ state was that these were held in place when the rear edge of the mount was peened over the rear lens, but at some time, maybe to clean between the lenses, this slight peening has been pulled back.

The eyepiece design is fairly standard. The last draw at the eyepiece contains two separate cartridges, one at each end, with two lenses in each. The lenses appear to be original, solidly mounted in their brass carriers that are threaded into the cartridges, but this section, which acts as a microscope, seemed initially to offer a very narrow field of view. This was then apparent when using the fully assembled telescope, when again the field of view was very narrow. The problem was identified as because of the positioning of the small orifice within the bottom cartridge. Somehow this had been loaded with the lenses in the wrong ends, and with the orifice positioned further away from the objective lens, the problem disappeared, but left a “jagged edge” appearance around the visible image disc. This was also eliminated, giving a much cleaner image, when the other cartridge closer to the eye was rotated and the lenses then replaced, although this orifice appears to be much larger and closer to the centre between these other two lenses.

dscn4338The mahogany barrel is fine, and has been improved by re-polishing; the connecting shoulders at the end of each draw are standard, with knurled end flanges. The screws holding the brass part of the telescope to the rear end of the barrel are not original; at the other end they are the originals: this brass mount is therefore slightly loose!

The objective lens has a push-on end cap present, the fairly standard design eyepiece cap has a flat end-face and includes an internal flip-across cover to protect the lens.

Acquisition #197

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One comment on “A Lincoln, with a triplet for the objective

  1. Hi,

    I was interested in your piece about your Lincoln three-draw telescope. I have such a telescope too. The inscription, which ends at the eyepiece, says “Lincoln London (both in italics) Newly Improved Day or Night”. I wonder whether it is newer than the one you have – perhaps made towards the end of Lincoln’s career.

    Regards,

    Robin Widdison.

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