Astrolabe: detail of inscription 'julius' in reverse

It is not currently known who made this unusually large astrolabe, but the design of the rete and the set of 'Italian' hour lines indicate that it could be Italian. An interesting feature on this astrolabe is provided by the fact that the calendar and zodiac on the back are set in reversed lettering. This was almost certainly meant for printing on paper, but it remains a mystery why the numbers alongside are not also reversed. The instrument has a specially shaped red leather case, which may well be original.

The throne has two lobes decorated with foliage motifs and a pierced hole on top to hold the shackle through which the suspension ring runs. Both the shackle and the ring have a bevelled section, similar to the Islamic astrolabes. The limb is riveted to the mater. There are three plates for the following latitudes: 36├òÔòØ/39├òÔòØ, 42├òÔòØ/45├òÔòØ and 48├òÔòØ/51├òÔòØ. The rete design is quite heavy and robust and includes flame-shaped star pointers that are very long. On the back of the instrument are four sets of concentric scales for degrees, the zodiac, the calendar and hours. Enclosed within these scales is a universal stereographic projection. The alidade is of the double alternate radius pattern.