| This 9.25" aperture optical tube gathers 33% more light than an 8" scope, providing brighter images of faint deep space objects. Its light-gathering ability is over 1125 times that of even the sharpest dark-adapted eye. The optical design uses a longer focal length primary mirror and lower magnification secondary mirror than a conventional SCT. This yields a flatter field of view at the focal plane. It also reduces optical aberrations during photography and when using wide field long focal length 2" eyepieces. An optimized baffle system further improves astrophotography by minimizing vignetting at the corners of a 35mm negative or large format CCD.
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 rugged aluminum optical tube is only 22" long and weighs only 20 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.
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.
A review of Celestron 9.25" optics in Astronomy magazine said the optics were “a real winner . . . (Jupiter’s) belts were simply dazzling, with subtle colors and the most tenuous detail seen steadily . . . (Saturn’s) rings were very impressive, and both Cassini’s Division and the C ring were easily visible . . . Deep sky objects were no less appealing . . . the Orion Nebula was wonderful, showing its gossamer clouds in all sorts of intricate contortions. Buried within the clouds, all four stars of the Trapezium sparkled, and even the more challenging E and F Trapezium members shown through . . . The telescope delivered consistently good images of these celestial gems – a sign of superb optical quality."
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 94x, with a 0.51° field that’s slightly larger than the full Moon.
A 4" wide dovetail slide bar runs the length of the tube for mounting the optical tube on a Celestron CGE or Losmandy GM8/G11 German equatorial mount. Optional 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
Lunar Photography