When/where was the Astrolabe improved upon?

Astrolabes have been traced to the 6th century, and they appear to have come into wide use from the early Middle Ages in Europe and the Islamic world. By about the mid-15th century, astrolabes were adopted by mariners and used in celestial navigation. The so-called mariner's astrolabe was later supplanted by sextants.

Ithink it’s bill gates.