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Whether you are a kid trying to set leaves on fire with the sun or a person looking for clues, you have most likely encountered a magnifying glass in some shape or form. In the modern world, it's one of those items that people take for granted, as if they've always existed. This article will give you a deeper insight into the world of... more »
Many people fear vision can be damaged by even the weakest lasers, such as those used in DVD drives. Of the four classes of lasers commonly used, two are officially considered harmless and two present either a genuine risk or the threat of immediate harm. Laser pointers fall into into a gray area of hazard, unlikely to cause damage... more »
The idea of a camera really existed before the technology had evolved sufficiently to create a substance to record the images. The camera obscura basically was a camera before the advent of film. The basic principals of this device---described in the 10th century by Ibn al Haitam, an Arab scholar---were expanded upon to create the... more »
A switch is a mechanical device that completes or breaks the flow of electricity through a wire or circuit. A limit switch is a special type of electromechanical switch used in applications where an electrical circuit must be "opened" (stopping the flow of electricity) or "closed" (allowing electricity to flow) when a mechanical... more »
A telephoto lens is any lens that contains a grouping of telephoto elements. This results in a lens with a long focal length, such that the lens itself is shorter than its own focal length. Telephoto lenses can be used to magnify distant subjects or to achieve zoom effects. more »
Observing the stars is a hobby that requires good equipment if you plan on getting the most out of it. Astronomy can be done from home or while... more »
A telescope allows you to explore the skies and see well beyond the capacity of the human eye. The telescope has certainly come a long way from... more »
You're on an Audubon chapter outing to nab some new birds, and your viewfinder captures a thumb print. Perhaps you're at a desert star party for... more »
All telescopes, other than some tabletop or simple refractor types, need a sturdy tripod for both security and optimal viewing. Most sizable... more »
Telescopes are sold with a variety of features that affect price. Besides aperture size and magnification, the telescope's movement controller... more »
A telescope is an instrument designed for the observation of remote objects by the collection of electromagnetic radiation. The first known practically functioning telescopes were invented in the Netherlands at the beginning of the 17th century. "Telescopes" can refer to a whole range of instruments operating in most regions of the electromagnetic spectrum.
The word "telescope" (from the Greek tele far and skopein to look or see; teleskopos far-seeing) was coined in 1611 by the Greek mathematician Giovanni Demisiani for one of Galileo Galileis instruments presented at a banquet at the Accademia dei Lincei.Sobel (2000, p.43), Drake (1978, p.196)Rosen, Edward, The Naming of the Telescope (1947) In the Starry Messenger Galileo had used the term "perspicillum".
History
The earliest evidence of working telescopes were the refracting telescopes that appeared in the Netherlands in 1608. Their development is credited to three individuals: Hans Lippershey and Zacharias Janssen, who were spectacle makers in Middelburg, and Jacob Metius of Alkmaar. Galileo greatly improved upon these designs the following year.
The idea that a mirror could be used as an objective instead of a lens was being investigated soon after the invention of the refracting telescope. The potential advantages of using parabolic mirrors, primarily reduction of spherical aberration with no chromatic aberration, led to many proposed designs and several attempts to build reflecting telescopes.Attempts by Niccolò Zucchi and James Gregory and theoretical designs by Bonaventura Cavalieri, Marin Mersenne, and Gregory among others In 1668, Isaac Newton built the first practical reflecting telescope that bears his name, the Newtonian reflector.
The invention of the achromatic lens in 1733 partially corrected color aberrations present in the simple lens and enabled the construction of shorter, more functional refracting telescopes. Reflecting telescopes, though not limited by read more at » http://en.wikipedia.org/wiki/Telescope
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