How to design and use the ZARQALE
Abu Ishaq Ibrahim ibn Yahya Al-Zarqali, )"Arzachel" to Latin Europe), (1028–1087 AD), was a leading Islamic mathematician and the foremost astronomer of his time. He flourished in Toledo in Andalusia, now Spain. He constructed a flat astrolabe, called ZARQALE , that was 'universal,' for it could be used at any latitude. It was like an astrolabe without rete and climates, but could be used an astrolabe's table of horizons.
In zarqale the celestial sphere is stereographically projected on the plane. And vision point is in vernal point. The latitude is the angle between alidade and celestial equator. And alidade is edline of horizon. Application of zarqale is as astrolabe's table of horizons but easier to use.
Presented by Safaei, Iraj; International Congress of 750th Anniversary of Great Scientist: Khaje-Nasirodin Toosi, 21-23 February, 2009, Tehran, Iran.