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Aperture mask
(Preview)
The front dust covers on most telescopes have a secondary light reducing aperture. The aperture mask is used to stop down the telescope's aperture to a smaller diameter for looking at the moon, bright objects or daylight viewing. A neutral density filter is commonly used instead of using an apertur...
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Meade Series 4000
(Preview)
Meade Series 4000 and 5000 eyepieces, filters, barlows Reviews on: 6.4, 9.7, 12.4, 15, 20, 26, 32, 40, Arcturus 20/30 2" filters, 1 1/4" filter, Barlows
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Polarizing filter
(Preview)
A polarizer is an optical filter that passes light of a specific polarization and blocks waves of other polarizations. It can convert a beam of light of undefined or mixed polarization into a beam with well-defined polarization. The common types of polarizers are linear polarizers and circular po...
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Ultra High Contrast Filter
(Preview)
The narrowband UHC filter, like the O-III filter, isolates the two doubly ionised oxygen lines (496 and 501nm) in addition to the hydrogen-beta line (486nm) emitted by planetary and most emission nebulae. This filter permits superb views of objects like the Orion, Lagoon, Swan and other extended...
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Parfocal Rings
(Preview)
A small tip to make some of your different branded eyepieces parfocal, is to manufactures some spacer rings by either gluing together a long strip of paper, or gluing strips of thin plastic that overlap or are laminated. These rings can then be slipped over the silver barrel of the eyepiece. The width...
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Orthoscopic Eyepieces
(Preview)
These Abbe-type orthoscopic oculars are good value for anyone seeking a high-contrast planetary eyepiece. These orthoscopic eyepieces are a four-lens design, and feature excellent contrast, flat fields, superior colour correction, and freedom from scattered light. The chrome-plated bra...
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Lowest magnification eyepiece
(Preview)
What is the largest (low magnification) eyepiece you can use with a telescope? To figure out the minimum magnification of a telescope, just divide the aperture in mm by 5 or 7 (older observers have a 5mm exit pupil size, younger observers have a 7mm exit pupil size). Which reversed, is the same as div...
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Sky-Watcher Long Eye Relief (LER) Eyepiece
(Preview)
Sky-Watcher Long Eye Relief (LER) Eyepieces These multi-coated eyepieces provide a generous 20mm eye relief, and all focal lengths including the 2mm model feature particularly wide diameter eye lenses for maximum viewing comfort. These eyepieces are especially valuable for spectacle wearer...
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Sky-Watcher SP Series Super Plossl 17mm Eyepiece
(Preview)
Sky-Watcher 'SP Series' Super Plossl 17mm Eyepiece This 1.25" (31.7mm) medium magnification eyepiece is well made and will provide good views of deep sky objects and open clusters. As to be expected there is a edge to edge pinpoint images and a nice 52 degree field of view. The eye relief is gene...
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SkyWatcher 25mm Plossl
(Preview)
SkyWatcher Plossl 25mm Focal Length: 25 mm Barrel Size: 1.25 Apparent FOV: 50.0 degrees Eye Relief: 22 mm Elements: 4 Field Stop Dia: 21.2 mm (?) Fully coated, and lens edges are blackened to reduce light scatter and maximise contrast. Threaded for use with 1.25&...
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Field of view
(Preview)
Apparent Field and True Field of view Telescope eyepieces determine the true field of view you see in the sky. To calculate the true field of view (in degrees °, divide the telescope eyepiece field stop diameter by the telescope's focal length and multiply the result by 57.3 (the quotient of 180 divid...
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Sky-Watcher APEX 28mm Eyepiece
(Preview)
SkyWatcher 2" APEX 28mm SkyWatcher 2" Kellner eyepieces offer a wide field of vision and excellent price to performance ratio. The 2" 28mm eyepiece is multicoated and offers excellent contrast and sharpness up at the outermost edge of the eyepiece. This eyepiece is recommended f...
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