Gilbert & Wright scope, circa 1800

Another telescope that came from the ‘Navigation Warehouse’, at 148 Leadenhall Street, London, at around 1800. See the previous comments about the people working there in the story about the Gilbert telescope, loaded onto this website on 24 Dec 2016. This was the place to go to, if you wanted the best in telescope making expertise for a particular duty, whether astronomical or nautical.

DSCN5386

In fact Gilbert worked in the partnership Gregory, Gilbert & Wright – from 1790-93. This telescope however is labelled as from the Gilbert & Wright partnership, which is quoted to have operated between 1790 and 92, and again between 1802 and 1805: in both periods they were based in the Navigation Warehouse.

The design is unusual, for the date, which is 1790-1805, 210 to 223 years ago. It is presumably a specially commissioned unit for a specific task, ie it was custom built for one of their customers, to his specification.

Who was the Customer?

This telescope is a two draw, completely brass unit. It is large in size, being 37.75” (96cms) long when fully extended: the length when focussed is considerably shorter, at 30.5” (77.5cms). This does mean that completely extended, it will give a focus on an object about 5 feet away from the objective, if you might wish to do that! But an advantage of the travel of the first draw is that there is around 1cm of movement where a distant object remains in a fairly good focus to the observer. The OD of the objective lens holder is nearly 2”, actually 4.9cm.

DSCN5384

Fully closed up the length is 15.25”: there is no sunshade or lens cap to protect the objective lens. On the eyepiece there is a slider that moves across the lens aperture: the second smaller aperture in the slider appears to originally have had a lens or filter mounted in there. Possibly located here was a deep red ruby filter (which restricts the light passing through to the eye, and so allows the telescope user to look at the edges of the sun, or at sunspots). Whether this means it was a telescope for use in an Observatory or similar I’m not sure. The generally ‘unfinished’ nature of the construction, with no protective covering on the barrel, no sunshade etc, might also imply it was not intended for outdoor (ie shipboard) use.

The Engraving

Another possible use might have been as a “lower magnification” aiming telescope, to be attached to a larger magnification scope in an Observatory. There are no obvious mounting points for this telescope, so it must have been strapped in place in some way. But the interesting positioning of the words engraved on the first draw, around the eyepiece, implies that the normally expected reader was maybe looking normally downwards, towards the top of the eyepiece: the words are then written horizontally, to this view, on one side of the draw, but around the curve of the brass tube.

DSCN5383The actual engraving says

Gilbert&White

London

Improved Telescope

…and the positioning on the first draw can be seen from the photograph.

Further data

Inside the first draw, the two eyepiece lens cartridges are fairly conventional in design: the first one (near the eyepiece) is engraved along the length with the words “SMALLEST POWER”. Presuming that another cartridge of higher power was supplied for the telescope (a standard approach with astronomical instruments) then this would explain the need for the first draw to be pushed in a long way to achieve focus – the other (missing) eyepiece might need to work with a focal point much further out.

Each draw is marked with an arrow, plus there are two arrows on the main barrel, pointing towards the objective. In my view this indicates the desirable orientation (rotation position) of the two draws, to get the parts of the telescope lined up in the original, ‘ex-factory’ setting.

The telescope was bought on Ebay in October 2016, for £87 including carriage, and there were no other bidders. Whether it is relevant I don’t know, but it came from Dorchester. Obviously there were not many people interested in a curious design of a 215 year old telescope! It did have a well-respected name….in a curious orientation, which is why I chased it.

Accession Number #293.

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