The
'tympan' on
this instrument is, in fact, the globe on which the
almucantars
and
azimuths
have been engraved and over which the cage-style
rete
rotates. In other words, the tympan is the body of the
instrument. The body of the instrument is hollow and screws
together at the equatorial line. The
meridian
line, in the northern hemisphere, is punctuated with holes
that were used to hold the rete in place at a given latitude.
A simple
pin would
have passed through the hole in the rete and provided the
axis of rotation through the pole of the
ecliptic.
Almucantars
| Divisions |
Labelled |
Style |
| Divided every 2° from 0° to 90° |
|
Plain line. |
| Divided every 5° from 5° to 90° |
Labelled every 5° with (Abdjad)
numerals |
Plain line. |
Azimuths
| Divisions |
Labelled |
Style |
| Divided every 10° |
Labelled every 5° with (Abdjad)
numerals |
Plain line. |
Circles
| Type |
Labelled |
Style |
Notes |
| Equator |
|
Plain line. |
Bears the number labels for the azimuths, which are
damascened silver. |
| Equinoctial colure |
|
Plain line. |
This line is damascened silver. |
| Solstitial colure |
|
Plain line. |
This line is damascened silver. |
Lines
| Type |
Labelled |
Description |
| Unequal hours |
Numbered (Numbers in Damascened script) |
(Abdjad), Plain line style. |
Inscriptions
| Transcription |
Translation |
Type |
| عمل موسى سنة ص ف ه |
The work of Mūsa. Year 885 |
Maker's signature |
| المشرق |
East |
Direction |
| المغرب |
West |
Direction |
| الجنوب |
South |
Direction |
| الشمال |
North |
Direction |