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Eyepiece lens

Inv. 2584 V.12 Eyepiece lens 1640-1660 [attr.] Ippolito Francini or Evangelista Torricelli or Jacopo Mariani Glass, wood, paper Diameter 44 mm

Description Plano-concave eyepiece lens, with cracked glass, mounted in a wooden ring covered with paper. The diameter of the lens is 30 mm, the aperture 24 mm, the focal length -200 mm (the negative focal length means that the lens is diverging). On the ring can be read "B: 10", indicating that it was to be combined with an objective of 10 braccia (corresponding to 5840 mm). Intended for very powerful instruments, this type of eyepiece was used in the years between 1640 and 1660. The lens is of Florentine origin, as can be deduced from the use of a measurement in braccia. Moreover, the ring and the inscription similar to lenses V.3 and V.5 suggest an attribution to Evangelista Torricelli or other Florentine opticians such as Ippolito Francini and Jacopo Mariani.