Astrolabe: mounted reverse

It is believed that this astrolabe was made in the early 20th century by an amateur astronomer or enthusiast for antique instruments and there is a German astrolabe that is similar to this one, made in Hamburg in 1608 and signed 'Christoph Magnus N.F.', that may have served as a model. Several aspects of the NMM's instrument substantiate this hypothesis. The shape of the rete and the arrangement on the back are reminiscent of late-medieval astrolabes; but the form of the stamped Arabic numbers and the letter shapes of the Latin alphabet are clearly not medieval. What's more, there are no star names alongside the star pointers, only stamped numbers.

The mater consists of a thin plate, without a thickened limb. Three lobes spring from it, with the larger, middle one pierced so that a ring can run through it, which, in turn, holds the suspension ring. The design of the rete is very simple: a straight equinoctial and solstitial bar, with the circles of the ecliptic and the equator. On the back of the instrument is a combined scale for degrees and the zodiac and a calendrical scale. The rest of the back is divided into two halves: the upper half shows the arcs for unequal hours and the lower half contains a shadow square.