| The Celestron C8 was the first Schmidt-Cassegrain telescope available to amateur astronomers. This 8" f/10 optical tube is the direct, but much improved, descendent of that original astronomical triumph. The rugged aluminum optical tube is only 17" long and weighs only 13 lbs., making it easy to transport and set up. An optional focal reducer (#8325) is available to bring the focal ratio down to a fast f/6.3 for CCD and 35mm photography.
Advanced Starbright XLT multicoatings are standard equipment. This coatings package includes high reflectivity multilayer aluminum mirrors enhanced with titanium dioxide for high reflectivity, plus a unique combination of magnesium fluoride and hafnium dioxide antireflection coatings on both sides of the Schmidt corrector lens. The corrector lens itself is made of high transmission water white float glass instead of conventional soda lime glass (which has 3.5% lower transmission) used in other telescopes.
Starbright XLT multicoatings visibly increase the contrast on subtle lunar, planetary, and nebula details when compared with a scope with standard multicoatings. They also give you higher light transmission for brighter deep space images and shorter exposure times during CCD and 35mm photography. Across the total visual/photographic spectrum from 400nm to 750nm, independent laboratory tests show the new Starbright XLT coatings are 16% brighter overall than even the original industry-standard Starbright multicoatings.
The optics are hand-figured, a complex optical procedure done on a commercial basis only by Celestron. Four separate optical tests are made on the optics, using a double-pass laser autocollimator – an Airy disc inspection, a test for spherical aberration by examining the diffraction images on both sides of focus, a Ronchi grating test, and a knife edge test. Using the tests as a guide, a skilled optician fabricates a precision pitch lap and delicately hand polishes the secondary mirror to smooth the optical figure and compensate for any small zonal defects. Done a few strokes at a time, and testing constantly to evaluate their effect, this final hand-figuring can take hours. But, when it is finished, the guaranteed diffraction-limited optical performance makes every tedious hour of hand-crafting well worth the effort.
The optical tube comes with a 6 x 30mm straight-through achromatic finderscope and mounting bracket. The finder has a wide 7° field of view. It focuses by loosening the trim ring behind the objective lens cell, screwing the lens cell in or out to focus, and tightening the trim ring to lock in the correct focus. Also included is a removable 1.25" visual back that holds visual and photographic accessories such as a star diagonal, tele-extender, etc. A 1.25" prism type star diagonal is also standard, as is a 1.25" 25mm Plössl eyepiece. This eyepiece provides a magnification of 81x, with a 0.59° field that’s almost 20% larger than the full moon.
A 1.75" wide dovetail slide bar runs the length of the tube for mounting the optical tube on a Celestron CG-5, Advanced Series Go-To, or Celestron/Vixen Great Polaris German equatorial mount. split mounting rings are also available to put the tube on another mount of the buyer’s choosing. Dust covers for the optics complete the supplied accessories.
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Terestrial Photography
