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Topic: Refractors

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	Illumination apparatus for ophthalmic refractors - Patent 5281984
		The refractor of claim 1 in which said light guide first transparent output is configured as a Fresnel lens of circular peripheral extent substantially encircling said cylinder axis scale; and said second transparent output is configured as a Fresnel lens configured to illuminate said cylinder power readout.
		The refractor of claim 8 in which said light guide includes an integrally formed thin portion extending outwardly from said inwardly extending cavity portion to a third transparent output positioned in adjacency with said spherical power readout and configured to transmit light thereto propagated from said light source.
		Refractors typically are fashioned comprising right and left batteries, each having an eye position for the patient before which any of a broad variety of disk-mounted testing lenses may be positioned.
	www.freepatentsonline.com /5281984.html (4942 words)

	spacegazer - Refractors
		Refractors are very robust in the sense that they do not normally require adjustment of the optics in order to put them back into alignment.
		Achromatic and apochromatics lenses are quite expensive to produce, and refractors are therefore the most expensive type of telescope in relation to their aperture.
		Refractors are the most robust telescopes, very easy to use, and therefore very suitable for novice astronomers.
	www.spacegazer.com /refractors-g.asp (456 words)

	Refractors
		Zero or two mirrors, as in straight through a refractor and a reflector: The image is upside down and backward.
		Refractors look like the classic telescope, and are in fact directly related to the first telescope to be pointed toward the heavens by Galilio in 1609.
		For this reason, a refractor of 6 inches diameter is very big and heavy compared to its counterpart, the reflector.
	www.starstuff.com /refractors.htm (410 words)

	Refractors
		Refractors can transmit 90% or more of the light they collect, compared with the 77% to 80% transmission of reflectors, and 64% to 75% of catadioptrics.
		With favorable seeing conditions, refractors can reveal subtle lunar and planetary features with a wider and more easily observed contrast range, and with more sharply etched detail, than is possible with the light-scattering optics of many larger reflectors and catadioptrics.
		The relatively small aperture of a refractor is therefore an advantage for this kind of observing, as there is less glare from the planetary surfaces to wash out detail.
	members.aol.com /nlpjp/refract.htm (691 words)

	Starizona CCD Guide - Refracting Telescopes (Site not responding. Last check: 2007-10-21)
		When light passes through a refractor lens, it is bent to reach a focus point at the back of the telescope.
		Most refractors are designed to eliminate (or minimize) chromatic aberration over the wavelengths to which the human eye is sensitive.
		Refractors over 7" in aperture are also rarely manufactured and are large and unwieldy instruments.
	www.starizona.com /ccd/equipbasicsref.htm (1060 words)

	Telescopes Astronomy science refractor, achromatic apochromatic
		Refractors gather more light than reflectors of the same size, but because of their cost mainly, they are not made to the same sizes as reflectors.
		So most refractors won't gather as much light as big reflectors, but this is not neccassary for viewing the planets because they are already very bright.
		This is where the curvature of the lens causes differences in distance between the center of the lens to the focus point, and the outer edges of the lens to the focus point, once again giving a poor image.
	www.angelfire.com /stars3/telescopes/telescopes013.htm (411 words)

	Celestron Refractors
		The equatorial mounts offered with the early refractors was the same heavy duty tripod mounted "Polaris" GEM used on the C6 reflectors.
		A 4" refractor with the same accessories, called the C100, was a 102mm f/12.7 optical tube mounted on a simple but sturdy alt-az mount.
		Building on the success of other high quality refractors, a line of telescopes with a flourite element in the lens was introduced that same year.
	home.att.net /~telescopebluebook/refractor/celestron.htm (581 words)

	Howstuffworks "How Telescopes Work"
		Refractors are the type of telescope that most of us are familiar with.
		Achromatic refractors use lenses that are not extensively corrected to prevent chromatic aberration, which is a rainbow halo that sometimes appears around images seen through a refractor.
		Refractors have good resolution, high enough to see details in planets and binary stars.
	www.howstuffworks.com /telescope2.htm (381 words)

	Refractors (Site not responding. Last check: 2007-10-21)
		Because of this, (good quality) refractors are renowned for their high contrast, crisp images.
		An apochromatic refractor is one where false color is corrected at three wavelengths - therefore apochromats are superior to achromats in terms of false color.
		Per inch of aperture, refractors are the most expensive design of the three we cover.
	astro.gpsrevs.urlq.net /refractors.htm (321 words)

	Refracting Telescopes (Site not responding. Last check: 2007-10-21)
		Refractors are ideal telescopes for terrestrial viewing too, when outfitted with an image-erecting prism.
		Refractors are compact and lightweight in smaller apertures, and thus are highly portable.
		Also unlike reflector or catadioptric telescopes, a refractor has a clear aperture, that is, there's no secondary mirror to obstruct any of the incoming light and degrade the image.
	www.twcac.org /Tutorials/refracting_telescopes.htm (305 words)

	Refracting telescope (Site not responding. Last check: 2007-10-21)
		A refracting telescope (refractor) is a telescope which uses lenses to refract light.
		This refraction causes parallel light rays to converge at a focal point; while those which were not parallel converge upon a focal plane.
		A refractor telescope is a type of optical telescope that refracts light through a pair of lenses on either end of the telescope.
	www.sciencedaily.com /encyclopedia/refracting_telescope (364 words)

	Refractor Telescopes (Site not responding. Last check: 2007-10-21)
		Refractors were the initial instruments of astronomy, and though at times surpassed in use by reflectors and other designs, have continued to garner many enthusiasts.
		In their simplest form they are the least expensive telescope to make with the automated tools available to industry today, which is chiefly why they have proliferated as entry level amateur telescopes for so long.
		At the other end of the spectrum, the highest quality refractors can be the most difficult to design and manufacture and as a result, are very costly.
	www.telescopebluebook.com /refractor/refractor.htm (326 words)

	INSTRUMENTS - Online Information article about INSTRUMENTS (Site not responding. Last check: 2007-10-21)
		average condition, is equal in light grasp to a first-rate refractor of to-in.
		Both the Dorpat and the Pulkovo refractors are defective in rigidity, especially in right ascension.
		The slow motion in right ascension is defective, being accomplished in the Dorpat refractor by changing the rate of the clock, and in the Pulkovo refractor by a handle which, when used, affects very injuriously the rate of the clock for the time being.
	encyclopedia.jrank.org /I27_INV/INSTRUMENTS.html (6915 words)

	Antique telescopes, brass refractors, antique scientific instruments.
		A bright star or planet viewed through a refractor with a single objective lens would have a bright red and violet halo around it.
		It was discovered that the longer a refractor was made, the closer the individual colors would tend to focus, supressing chromatic aberration.
		By the 21st century, telescope makers had discovered how to make a refractor focus all the colors of light very, very close to a single point--at least close enough that the human eye can no longer detect the halo of chromatic aberration.
	www.antiquetelescopes.org /17thc.html (803 words)

	Refractor (Site not responding. Last check: 2007-10-21)
		This is the design used in modern refractors.
		Refracting telescopes use lenses to gather light and focus it to the eyepiece.
		The objective lens is located at the front of the telescope and the eyepiece at the rear.
	www.starizona.com /basics/refractor.html (141 words)

	Orion Refractors (Site not responding. Last check: 2007-10-21)
		In the late 1980's they began to market a line of Japanese refractors under their own name.
		The TeleVista 60 was a 60mm f/11.7 refractor on an inexpensive alt-az mount with slo-mo in both axes.
		This too was a standard 60mm f/11.7 refractor on an inexpensive alt-az mount, but it had slo-mo in altitude only.
	telescopebluebook.com /refractor/orion.htm (441 words)

	Astro Physics Refractors (Site not responding. Last check: 2007-10-21)
		The Starfire line was officially introduced in 1987, but optical tubes of various sizes and focal lengths with the same technology were made in years previous to this.
		These refractors contained apochromatic doublet objectives from 4" to 7".
		It was available on either a heavy metal tripod or pier, and included a polar axis scope and a worm gear 12v.
	home.att.net /~telescopebluebook/refractor/astrophys.htm (287 words)

	Stellarvue 80mm Achromatic Refractors
		While the explanation of the optical design and performance distinctions between apochromatic and achromatic refractors is best left as an exercise for the reader, one additional important fact is that the former are usually far more expensive than the latter.
		Sharp high-contrast wider field-of-view images in a well made small aperture refractor can indeed be competitive with brighter images from larger aperture telescopes, for certain available celestial targets and atmospheric conditions.
		The 80/9D is my primary telescope for the Moon, planets, and Sun (with a suitable white-light filter), and is often placed on a motorized Celestron CG-5 mount connected to a wood (oak) tripod for stability and to maintain the desired subject in the field of view at higher powers.
	www.novac.com /resources/reviews/stellarvue80.php (1505 words)

	Camera & Photo - Refractors : StormLabs.com
		This compact short focus [f/5.9 - 355mm] apo refractor is the perfect eclipse telescope and with its optional Triplet Reducer [f/4.4 - 264mm] is a great...
		Refractor Telescope 150mm diameter (6"), Focal Length 1200mm Achromatic objective Metal Tube assembly, Eyepiece holder 1.25".
		This refractor is packed with great features and excellent optics including our high quality ED glass.
	www.stormlabs.com /Cameras/Refractors/Browse/499152/page/3/sort/66/thumbnails/False (992 words)

	All About Refractors (Site not responding. Last check: 2007-10-21)
		Refractor telescopes (also known as dioptrics) are probably what most of us think of when we hear the word "telescope." Refractors have a long, thin tube in which light passes in a straight line from the front objective lens directly to the eyepiece, at the opposite end of the tube.
		The 60mm (2.4") refractor is the most popular telescope size for beginning astronomy enthusiasts and for casual gift-giving.
		Celestron's 80mm and 102mm refractor models are top choices for beginning observers who want to start with a more powerful telescope and for intermediate level astronomers.
	www.americansupply.net /about_refractor_telescopes_.htm (490 words)

	Cleaning mirrors lenses optics Telescopes Binoculars Refractors Reflectors
		Cleaning optics whether binoculars, refractors or reflectors can reduce the light gathering power by scratching or removing the enhanced coatings placed on them to improve their performance.
		Refractor and binocular lenses are more forgiving than mirrored surfaces.
		However it is quite easy to remove or scratch the coloured enhanced coatings on binoculars and refractors just by wiping with a soft cloth too hard.
	www.telescopes-astronomy.com.au /telescopes061.htm (398 words)

	Refractors versus Reflectors (Site not responding. Last check: 2007-10-21)
		We'll begin our survey with the classic achromatic refractor which, as it happens, was the first type of telescope that I tried for CCD imaging.
		All achromatic refractors suffer from considerable secondary chromatic aberration, but the lenses are designed to minimize the visual impact.
		Furthermore, unless you plan to use a CCD that is large (i.e., more than 10 millimeters across the diagonal) or one that has small pixels (i.e., smaller than 10 micrometers), or have a Newtonian that is faster than f/4, the coma blur simply doesn't get large enough to be visible.
	www.willbell.com /cookbook/refrrefl.htm (1195 words)

	Small Refractors, Beginners, and Messier Hunting (Site not responding. Last check: 2007-10-21)
		Good small refractors are costly -- an altazimuth Vixen 80 mm runs nearly $600 from Telescope and Binocular Center (including shipping), a fair bit more than the Dobsons I mentioned earler.
		At f/8, a 32 mm Plossl in a 1.25 inch focuser would give a reasonably large exit pupil (4 mm) and a field not so narrow to be tunnel-like.
		Vixen makes a 102 mm f/9.8 refractor whose conventional-doublet objective shows acceptably little color; such a design should work well at 80 mm f/8.
	nineplanets.org /psc/or/j33.html (509 words)

	Introduction to chromatic abberation in refractors
		The popularity of high-quality refractors draws attention to color correction in such instruments.
		If you adjust an eyepiece to be in focus half way between red and blue, at the 1000 mm position, images of bright stars will be surrounded by an overlapping violet glow - the out-of-focus red and blue images mixed - that is 7.5 mm divided by 10, or 750 microns in diameter.
		I sometimes think I see this effect in my 98 mm f/6.7 Brandon refractor, whose objective is an one of Roland Christen's early triplet apochromats.
	www.maa.mhn.de /Scholar/chromatic_aberration.html (1878 words)

	All A: refractors Z: refractors (Site not responding. Last check: 2007-10-21)
		Refractors (also known as dioptrics) are what the average person identifies with the word "telescope...
		In its basic form, as Galileo used it 400 years ago, it is simply a curved lens which focuses light to a point.
		Newtonians and high-resolution achromatic refractors or Schmidt-Cassegrain, mounted on the...
	www.davidchuk.com /refractors.html (224 words)

	The first refractors ever made were not achromatic
		The first refractors ever made were not achromatic.
		The five dollar toy telescope of today is of this simplest variety which is referred to as a Galilean refractor.
		To their credit, all commercial 2.4 inch refractors are achromatic.
	www.singularsci.com /ScopeTypes4.htm (484 words)

	Telescope.org Sponsored by ScopeTronix
		There are three major types of telescopes available to the amateur astronomer: refractors, reflectors, and catadioptric telescopes.
		Refractors were the first form of telescope invented in the early 1600's.
		Because refractors don't have any small mirrors in their light path they provide very sharp images.
	www.scopetronix.com /telescopes/ttypes.htm (706 words)

	Binoculars/Scopes, Telescopes, Refractors - buy online (Site not responding. Last check: 2007-10-21)
		The ED SS refractors feature a 2-group 3-element optical design with ED (extra-low-dispersion) glass to dramatically reduce the secondary spectrum and...
		The ED S apochromatic refractor features Extra-Low Dispersion (ED) glass in its objective lens to suppress chromatic aberration to a virtually invisib...
		Vixen achromatic refractors provide pinpoint images of the stars as well as sharp images of the Moon and planets.
	www.photo-items.com /binoculars_scopes/telescopes_refractors4.htm (298 words)

	Coulter Optics - Refractors (Site not responding. Last check: 2007-10-21)
		102mm X 1000mm Refractor with its heavy-duty German Equatorial Mount is a precise, capable and impressive yet affordable instrument for the advanced astronomer.
		Short Refractor is an unusual departure from the common long focal length refractor.
		Refractor is mounted on our strong, stable Standard German Equatorial Mount for maximum economy and value.
	www.telescopesa.za.org /~mike/CatalogCoulterOpticsRefractor.htm (770 words)

	Vixen Refractors are excellent astronomical instruments. (Site not responding. Last check: 2007-10-21)
		A80MWT SX-Trim on Sphinx Mount - 80mm Achromatic Refractor
		ED80SWT SX-Trim on Sphinx Mount - 80mm Apochromatic Refractor
		A102MWT SX-Trim on Sphinx Mount - 102mm Achromatic Refractor
	www.thescienceshop.ca /vixen_refractors/vixen_refractors_splash.htm (336 words)

	Konus Refractors
		This 80 mm refractor is fast, sharp, and highly compact.
		This 90 mm refractor gives sharp, high contrast views of the planets and deep-sky objects.
		This pair of refractors give sharp, high contrast views of the planets and deep-sky objects.
	www.owlservices.com /refract.htm (449 words)

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