Tools utilizing a star chart include the astrolabe and planisphere. He used instruments such as the astrolabe and sextants to aide his studies of navigation. Additionally, al-Khwarizmi wrote about the astrolabe, sundial, and elaborated on Ptolemy's geometric model. He also wrote on mechanical devices like the astrolabe and sundial. The outcome was an Imperial order for globes, compasses, astrolabe and astronomical rings. Arab navigational tools like the astrolabe and quadrant were used for celestial navigation. The geared mechanical astrolabe was invented by Abi Bakr of Isfahan in 1235. The oldest rectangular astrolabe dates back to Babylonia c. 1100 BC. He wrote on grammar, astronomy, the astrolabe, etc. Chaucer's "Treatise on the Astrolabe" was written for Lewis. It was originally proposed by Ptolemy as a better kind of astrolabe. Vesper One commands Amy and Dan to find a stale orb, an anagram for astrolabe. They fly to Samarkand, Uzbekistan, to find the astrolabe. He developed key technologies including the equatorium and universal latitude-independent astrolabe. He also devised, with help from al-Zarqali, the universal astrolabe.