The very first telescopes were believed to have began to appear around the year 1608 and were credited to opticians Hans Lippershey and Zacharias Janssen as a type of spyglass. These early refracting telescopes consisted of a convex objective lens and a concave eyepiece and the telescope simply slid inside itself to focus.Galileo greatly improved upon this design and is often credited as being the first to invent the first astronomical telescope.. In 1611, Johannes Kepler described how a telescope could be made with a convex objective and eyepiece lens and by the year 1655 astronomers such as Christiaan Huygens were building powerful but extremely large and bulky Keplerian-design telescopes with compound eyepieces.
By the year 1616, Niccolò Zucchi had designed the first reflecting telescope, but the design was impractical. By 1688, Sir Isaac Newton had solved the problems of Zucchi’s reflector by adding a small flat diagonal mirror to reflect the light to an eyepiece mounted on the side of the telescope. During 1688, Laurent Cassegrain initiated the design of a reflector with a small convex secondary mirror to reflect light through a central hole in the main mirror. In 1733, Chester Moore Hall went into telescope history with the first achromatic lens refractor and John Dolland independently came up with the same design five years later producing telescopes and marketing them. John Hadley was working to improve reflecting telescopes in 1721 by creating larger paraboloidal mirrors, but it would be 1857 before Léon Foucault came up with a good process for coating them, known as silvering. Believe it or not, it would be 1932, before long lasting aluminized coatings on reflector mirrors would become a standard!
How does it work?
ReplyDelete