A substantial Islamic astronomical quadrant of quarter-circu...

A substantial Islamic astronomical quadrant of quarter-circular form, engraved on both faces with mathematical and astronomical scales and inscriptions in Arabic, characteristic of the western Islamic, or Maghribi, scientific tradition, the principal face is arranged as an astrolabic quadrant, with a stereographic projection comprising curved astronomical lines, graduated scales and computational divisions used for determining altitude, time and solar position. Among the inscriptions is خط الزوال (khațț al-zawāl), meaning ‘the meridian line’ or ‘noon line’, further markings appear to employ abjad numerical notation, in which Arabic letters carry numerical values, the reverse carries a finely divided sine-cosine or trigonometric quadrant, with a rectilinear grid and diagonal construction lines used for mathematical and astronomical calculations, the straight radius incorporates the sighting arrangement, with the plumb-line attachment at the ape, likely Morocco, late 18th century or earlier, 23cm wide

估價:$663.38

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