A poll in early telescopes provides an interesting read. Figured in 1722 joined John Hadley, an English mathematician, a form of the reflector of the telescope mirror in the style of Newton was apparently a result. This tool is a great feeling, and now turns to other producers were Newtonian reflectors, according to Hadley Technology, which was to eliminate spherical aberration, as has been revealed by extra-focal diffractionRings to take a star.
Hadley then turned to a design by James Gregory in 1726 and has produced an instrument a little 'more than 2 "in diameter and 12" focal length. This proved so successful that the construction was carried out by others.
Among these was James Short, both Newton and Gregorian produced in large numbers, from about 1732 until the time of his death in 1768. Observers bought his greatest tools, a tribute to his ability, and the smallesthave been marketed primarily under the needle and amateur astronomers.
The main attraction of the project was in direct Gregorian image there, that for terrestrial use. This fact influences the advantage over Newton's, despite the fact that his paintings must be pretty boring. Up to 19 century, but the Gregorian ridden a wave of popularity that any type of telescope known until relatively recent years, overwhelmed byFlood of amateurs who have poured Newton-design.
Since the invention of the telescope and the amazing discoveries of Jupiter's moons and rings of Saturn, the interest in astronomy had something contagious. Each new discovery has been given maximum publicity, stimulating demand for learning among those first-hand on this win heavenly miracle. It was not practical for the average person or to his speculum, but many fictionadjust the lenses in tubes, just as Galileo did 150 years ago. This was one of the first of the first telescopes.
Those whose means permitted bought telescopes, and envied the gentleman who was one of three or four cm opening through an artist had "exclusive". Measured, but, by today's standards, many of these were tiny reflectors. There is an (unknown manufacturer) in the collection of the Fugger of Augsburg, just 1 "in diameter and 6" focal length, which washidden in a walking stick! Eyepiece 1 / 6 "focal length or less were not uncommon.
The metal was used in these early stages is an alloy of copper and tin, the usual volume of about 75 to 25, which could be given a nice polish. But the metal had to work very hard, and a huge amount of work was involved in sanding and polishing of the curve. To facilitate the work, which ensures slices thin enough to approximate the curve were thrown on the curveto give uniform thickness and the compensation of temperature effects. Grinding tools of iron-like radius convex done with sandpaper, and sometimes sand. Polishing was done on a round field with rouge.
Manufacturers typically build their own machines to do the job of sanding and polishing. As it was necessary to the highest perfection that seems to have made a great final part of a short variant of stroke in an attempt to focus on polishing without guidancethe center. Critical review, was issued in doubt because of its rare nature, so far only be performed on a star. In specula reflectivity was only about 60 percent more efficient, and surface finish in a hurry, causing more severe loss of light. This meant frequent polishing and polishing Refiguring say.
It 'interesting that the prices for telescopes in this period, in the second half of the 18 st Century has been asked to investigate. Below arePrices and trained by some of the Gregorian made by Short, selected from his catalog. Newton in a similar format were only slightly lower price.
Diameter (cm) focal length (mm) price increases (guineas) *
1.1 3 18 3
1.9 7 6 40
4.5 24 90-300 35
6,3 100-400 36 75
18144800300-1.200
* An English gold coin issued until 1813, amounting to 21 shillings, about five dollars.
Early telescopes were certainlygaining popularity in this period.
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