An undated astrolabe by Hasan ibn Muhammad al-Shîrâzî

in good overall condition, 5 plates, areas of minor patination and pitting particularly to some of the plates, as viewed
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This is an unusual astrolabe, signed by a maker, Hasan ibn Muhammad al-Shîrâzî, that is, from Shiraz, who is previously unknown to us.

This work of his reveals some initiative as well as some incompetence. The former suggests an early date, possibly the 17th century, the latter a later one, possibly the 18th century.

The throne is decorated with floral fronds. The distinctive rete is ingeniously symmetrical, with certain minor stars included to achieve this. However, some of the stars are misnamed, for example, musalsala below the right horizon. The two little birds are also unhappily labelled. On the one above the middle it is the head that marks the star (al-nasr al-)wâqi', Vega, "the falling eagle", rather than the beak. The other bird above it is labelled dajâja, chicken, which name is usually used for the constellation of Cygnus, the swan, elsewhere in the sky; the beak of this bird touches the pointer for (al-)nasr al-tâ'ir, Altair, "the flying eagle". The left-hand outer rim of the rete has been broken off.

The mater is engraved with a gazetteer of 54 place-names, with longitude, latitude and qibla. The inscription written in exaggeratedly decorative kûfî script reads:

sana'hu Hasan ibn Muhammad al-Shîrâzî,

that is, "made by Hasan ibn Muhammad al-Shîrâzî."

The astrolabic markings on the five plates are for each 6° of altitude, with no azimuth circles. Those plates serving specific latitudes are as follows:

1a: 30° / 14h5m; 1b: 32° / 14h7m; 2a: 38° / 14h36m; 3a: 36° / 14h7m; 4a: 42° (actually 40°) / 13h54m; 4b: 38° (14h39m) / 13h54m and 45° / 15h25m; 5a: 30° (actually 32°) / 14h25m

Some of the latitudes are confused and the lengths of longest daylight are very confused. Plate 4b has two halves of different sets of markings. Plate 2b bears astrological scales using standard abbreviations for the names of the sun (s for shams), moon (r for qamar), and planets (always the last letter). Plate 5b has a set of concentric circles, roughly uniformly increasing in radius; these do not serve any astronomical purpose.

The upper back is marked for each 5° of solar altitude, subdivided into 1° intervals. Within these are two sets of incomplete trigonometric markings in each quadrant, horizontal on the left, vertical on the right. The crude markings on the alidade - for each 5 units up to 60 - are to be used with these. Below is a double shadow square to base 7 (aqdâm, feet) on the left and to base 12 (asâbi') on the right. The scales on the lower outer rim serve the same purpose, that is, to determine the shadows corresponding to solar altitudes on the upper scales.