اسطرلاب ِ خطی ostorlâb-e xatti
*Fr.: astrolabe linéaire*
A version of → *planispheric astrolabe* in which the
→ *celestial sphere* and the various circles of
altitude and declination are projected on to a line represented by a staff.
The staff is equivalent to the meridian
line and contains markings to indicate the centers of these circles
and their intersections with the meridian.
By attaching three ropes to the appropriate points
on the staff to act as radii, the circles and their intersections can
be reconstructed. One of the ropes was attached
to a plumb line. A scale giving
chord lengths in the meridian circle extended the linear astrolabe's
range of applications. It was invented by the Iranian mathematician and
astronomer Sharafeddin Tusi (*c*1135-1213), but no early example has survived.
Same as → *Sharafeddin's staff* and *Tusi's staff*. → *linear*; → *astrolabe*. |