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Description: | 2
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These 2 Glasses Marked T to be taken out when used at night.
The barrel of this non-achromatic telescope is made of vellum decorated with gold-tooled motifs that are now only just visible. The two draw tubes are also made of vellum but are not decorated. The brass fittings include a sliding eyepiece cover.
In the early 18th century it was only possible to make lenses with a relatively long focal length meaning that telescopes had to be very long - this example can extend to over 2000 mm. Stop lines have been marked on each draw tube to indicate its optimum working length.
An inscription on one of the tubes that holds the correcting lenses states, 'These 2 Glasses... to be taken out when used at night'. This would reduce the amount of light lost, but would also mean that the observed image was inverted.
AUDIT - item needs marking with its identity number. One unnumbered part.
Focal length; 75". O.G.diameter: 1.7".
M Bolt: use of brass suggests later
caption: Portable telescope
caption: Telescope - inscription | Publisher: | "http://collections.rmg.co.uk/" | Rights holder: | "Royal Museums Greenwich" | Subjects: | Gold tooling Vellum telescopes | Source: | Royal Museums Greenwich | Identifier: | http://collections.rmg.co.uk/collections... | Go to resource |
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