Though telescopes have a long history they were only produced in quantities to be widely available in the late 18th century.
Problems of lens polishing, lens composition, and manufacturing were slowly overcome and the telescope became a vital element of seafaring equipment. Superior optics meant that navigation hazards could be identified at longer distance, and in time of war and piracy it meant that approaching vessels could be recognized at longer distances. It also made the use of communications by signal flags practical.
Early telescope construction consisted of barrels constructed of leather, vellum, or wood with the lenses held in place by brass fittings. The one pictured below and found in the National Maritime Museum, Greenwich, London dates from 1775 and is made of mahogany. It measures 35″ closed and when open is 44″ long. The opening holding the objective lens is 66mm, about 2.5″, in diameter. Hardly something you’d want to climb into the rigging holding.
As the science of metallurgy advanced, the telescope barrels of brass became more common. This next telescope, also from the National Maritime Museum, dates from about 1800 and is leather-covered brass some 25″ long when closed and 29″ long when opened. The end holding the objective lens is 44mm or about 1.7″ in diameter.
In the case of the brass telescope, the handiness of lopping some 15 inches off the extended length is a radically reduced field of vision.
Another interesting innovation was the development of the night telescope, or night glass. Using a conventional telescope at night is difficult because the relatively small objective lens did not permit a lot of light to enter the tube and interior lenses which were required to correct the inverted image produced by a simple refracting telescope absorbed part of that light. The result was a telescope with a fairly large objective lens but which produced an image that was inverted,
The below example of a night telescope dates from 1810, it has a leather tube with brass fitting. It measures 28″ long closed and 34″ when extended. The end holding the objective lens is 82mm, or nearly 3.25″.
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I am a collector of British naval telescopes. I am looking for some source that references standard Admiralty patterns for manufacturers to use strting from the 1880′s onward. I would appreciate any suggestions
I’d suggest checking with the people at http://groups.yahoo.com/group/RoyalNavy_from_1789/ there are a lot of experts on the RN on the list, something which I don’t claim to be
I have a friend with an amazing collection. The store won’t be open until 1/10/10, but you can get a look at what he has online in the museum. It’s a gorgeous site. http://www.opticaliamuseum.com
I am trying to find some information on two telescopes we have .
First is a W.Watson & son –1916 ,No 5278
sighting telescope No4 Mk III with the
Goverment arrow . ex father-in-law .
The 2nd is a H . Hughes & sons Naval telescope of
my grandfathers No 417a/3969
I also have a H . Hughes & sons brass and leather naval telescope that beldonged to my grandfather. Unfortunately the lens at the end is missing. I would love to know what it looked like as I am thinking of looking for a specialist who could replace it.
Mine is engraves: H.(enry) Hughes and Son, 59, Fenchurch St., London. That was the makers address between 1879-1941.
Does anyone have information on the “Come Up” telescope that Jack Aubrey employs from the upper yards to determine if he is overtaking a prize? I cannot cite the volume in O’Brian’s series where this event took place, but the scope had two (2) images side by side of the chase. If one were overtaking, one of the images would superimpose (?) over the other or some such optical magic.
Google, Wiki, ePay, and Amazon have not been able to help me in finding information or sources about this fascinating piece of equipment.
Thank you
“What a fascinating modern world we live in!”
agreed! I also found a reference to this in Alaric Bond’s “The Jackass Frigate” and I can’t find any explanation or description of it… in fact the only reason I found this page is that it came back as a hit on “come up glass”!
http://www.tandfonline.com/doi/abs/10.1080/14786440508562460?journalCode=tphm12
” invented by the late Mr Ramsden It consists in applying a micrometer to a refracting telescope of about two feel long or to a day and night telescope”
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