Middleburg Netherlands 1608 spectacle maker Hans Lippershey applies to patent the first telescope; in 1609 Galileo uses this to observe that the uneven occlusion of light on the moon comes from mountains and craters and in 1610 discovers moons orbiting planet Jupiter. On from the Cassegrain and achromatic reflectors comes the production of paraboloidal mirrors in 1721 and the process of silvering glass mirrors was introduced by Leon Foucault in 1857. In the 19th century stellar spectra and different types of electromagnetic radiation with Friedrich Bessel in 1838 making the first direct measurement of distance to a star 61 Cygni by the parallax technique. In the 20th and 21st centuries the 100” Mount Wilson and 200” Mount Palomar Cassegrain reflectors are used to observe galaxies clusters then Hubble notices gravitational lensing and the 6.5 meter James Webb infrared telescope comes into use for estimates of mass and dynamical effects in superclusters.
