The instrument

Dynamic version

Telescope's components
1 Tube

Tube
The bearing structure is formed of 20 strips of wood, glued onto a sheet of paper and covered in red leather with gold tooling. At each end the strips of wood are left bare of the leather covering to allow the cylinders containing the optical parts to be inserted by pressure. The overall length is 835 mm.

2 Housing of the objective lens

Housing of the objective lens
The housing consists of a wooden cylinder, covered in the same leather as the tube, 45 mm long with outside diameter of 61 mm. One end is inserted by pressure into the tube, the other, with inside diameter of 52 mm, houses the objective lens, protected by a wooden ring.

3 Objective lens

Objective lens
This is a plano-convex (converging) lens with the convexity facing outside. It has a focal distance of 980 mm, a diameter of 37 mm and a thickness at the centre of 2.0 mm. A cardboard diaphragm limits the aperture to 15 mm.

4 Eyepiece tube

Eyepiece tube
It consists of a wooden cylinder, covered in the same leather as the tube, 40 mm long. One end is inserted by pressure into the tube, while the other, whose inside diameter is the same as the outside diameter of the eyepiece housing, allows the latter to slide in order to bring the object observed into focus.

5 Eyepiece housing

Eyepiece housing
Boxwood cap with internal and external thread. The internal thread serves to fasten the eyepiece holder to the retractable optical tube, while the protective cap screws onto the external one. The lens is inserted in the eyepiece holder, positioned 6 mm from the outer edge.

6 Eyepiece Eyepiece
The original eyepiece has been lost. It has been replaced by a biconcave lens with focal length of -47.5 mm (the minus sign indicates that the lens is diverging). Its diameter is 22 mm and its thickness at the centre 1.8 mm. A cardboard diaphragm limits the aperture to 15 mm.

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Dynamic version

 

 

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