But astronomers have since invented adaptive optics, a technique that measures the atmospheric turbulence above a telescope and continuously deforms its mirror to compensate.

For more than two centuries after Sir Isaac Newton invented the reflecting telescope - the type of telescope still used by most observatories - astronomers observed with their eyes.

The Eastern Han Dynasty scholar and astronomer Zhang Heng (78-139 AD) invented the first water-powered rotating armillary sphere (the first armillary sphere having been invented by the Greek Eratosthenes), and catalogued 2500 stars and over 100 constellations.

In the 14th century, the Syrian astronomer and timekeeper Ibn al-Shatir (1304-1375) invented a timekeeping device incorporating both a universal sundial and a magnetic compass.

Muslim astronomers also independently invented the celestial globe, which were used primarily for solving problems in celestial astronomy.

When the southernmost stars also were divided up, the whole situation became somewhat chaotic; various astronomers invented their own constellations, some of which were so small and so obscure as to be unworthy of separate identity.

Jean-Paul Fouchy, a mathematics professor and astronomer in France invented an octant in 1732.

A Belgian statistician and astronomer, Adolphe Quetelet, invented the index formula in the 1830s.