23. Galilean telescope
XVIIth cen. ?
author and place unknown
pasteboard, case in turned wood
length closed 18.3 cm, open 44 cm, diameter 3 cm
length case 22.3 cm, diameter 4 cm
[Inv. MdS-34]

"A hand-held telescope with well-turned granadilla case", says the inventory of 1746.
The tube of this classical Galilean-type small telescope is of glued pasteboard, made from waste-paper. The outside, green, has a gilded flower pattern.
The optical system is one of the more simple, comprising two lenses, one convergent (object lens), the other divergent (eye-piece). The image is thus virtual, straight and magnified. Only the object lens remains.

M. Calisi (1991), p. 26.
G.L'E. Turner (1991), p. 412 ff.
A. Van Helden (in M. Miniati, 1991), p. 65.