The most sophisticated and beautiful of the astronomical instruments, prior to the era of the telescope, was, undoubtedly, the astrolabe. In the 9th century, Arab astronomers improved the instrument by introducing angular scales and azimuth lines, while enriching their beauty. Combining a rudimentary observational tool with an elegant analog computer, astrolabes were used for various tasks from the calculation of time, measurements of heights (astrologers, landforms) to the making of horoscopes. The knowledge and use of the astrolabe expanded throughout the Islamic world for centuries before it reached Renaissance Europe.