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Lancashire Astroguy

Well done Google!

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Good on Google for celebrating today on their title page the birthday of one of the giants of 17th century astronomy and physics - Johannes Kepler. There is even an animation demonstrating accurately not just the first but also the second law of planetary motion!

Whilst most of the general public are familiar with Galileo and Newton, the name of Kepler will be less well known to them. Yet he was a mathematical genius whose work on the motion of planets finally buried the geocentric theory forever, and led directly to Newton's formulation of the Universal Law of Gravitation. Indeed, in his discovery of the third law of orbital motion (period squared proportional to radius cubed), Kepler must have only been a hairs breadth away from deriving the Law of Gravitation himself. Certainly everyone today who uses satellite technology in their everyday lives (which lets face it is pretty much everyone!) owes a debt of gratitude to Kepler, as well as Newton, for making this possible.

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I liked the one they did about alien abductions not so long back, I think its theme was Roswell :smiley:

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Kepler one of the greats of telescope invention.

The Keplerian Telescope, invented by Johannes Kepler in 1611, is an improvement on Galileo's design. It uses a convex lens as the eyepiece instead of Galileo's concave one. The advantage of this arrangement is that the rays of light emerging from the eyepiece are converging. This allows for a much wider field of view and greater eye relief, but the image for the viewer is inverted. Considerably higher magnifications can be reached with this design, but to overcome aberrations the simple objective lens needs to have a very high f-ratio (Johannes Hevelius built one with a 45 m (150 ft) focal length, and even longer tubeless "aerial telescopes" were constructed). The design also allows for use of a micrometer at the focal plane (used to determining the angular size and/or distance between objects observed).

Edited by Monty

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