Portable telescope

The barrel and six draw tubes of this non-achromatic telescope are made of vellum with fittings of lignum vitae, including a screw-on cap for the objective lens. The barrel is also decorated with gold-tooled motifs and has the maker's name stamped on it: 'MADE BY WILL LONGLAND AT THE SHIP IN CORNHILL LONDON'.

Early telescope lenses suffered from the appearance of coloured fringes, a problem that could be reduced by using lenses with long focal lengths. This meant, however, that the telescopes had to be very long - this telescope can be extended to over 1.5m. To make them compact and light enough to carry, they were made of several draw tubes, whuch were typically of papier-mâché covered in vellum. This example has a black line on each draw tube to indicate its optimum working length.