Celestron 8" EdgeHD Optical Tube, CGE/Losmandy Dovetail

The EdgeHD high definition flat field optics of this Celestron 8" EdgeHD optical tube make true astrographic-quality 8" optics truly affordable.

The compact and easily transportable Celestron 8" EdgeHD optical tube has new and unique 8" aperture aplanatic (free from coma and corrected for spherical aberration) EdgeHD high definition/high contrast Schmidt optics. The advanced EdgeHD optical system uses a dedicated dual-element field flattener lens made from premium Schott optical glass in its central baffle tube to reduce off-axis coma and produce aberration-free images across a wide 42mm image circle (as large as the diagonal of a 35mm negative or large format CCD chip and ideal for astrophotography).

In addition to reduced off-axis coma, the EdgeHD optics deliver an astrograph-quality focal plane more than three times flatter than standard Schmidt-Cassegrains and dramatically flatter than competing coma-free designs. Stars are smaller and more concentrated, creating brighter images and allowing you to see down to a fainter magnitude than other equally-sized telescopes. With EdgeHD optics, you see sharp point-like stars to the very edges of some of the largest CCD and DSLR chips available today.

For the ultimate in brightness and contrast, the 8" EdgeHD optical tube has state-of-the-art Starbright XLT multicoatings. Its light grasp is almost 850 times that of even the sharpest dark-adapted eye, revealing to your eye and camera star clusters, nebulas, planets, and galaxies in amazing detail. The Fastar-compatible optical tube even allows imaging down to an incredibly-fast f/2 focal ratio using optional accessories.

This Celestron Optical Tube's Optics . . .

EdgeHD aplanatic Schmidt-Cassegrain optics: 8" aperture (2032mm focal length f/10). Guaranteed diffraction-limited optical performance, free from coma and corrected for spherical aberrations (aplanatic design). Dual-element field flattener lens built into central baffle tube. The 17" long aluminum optical tube has a large handle on the rear cell and weighs only 14 pounds, making it easy to transport and assemble the optical tube to a mount in the field. For more details, click on the "EdgeHD optics" link in the support tab above.

Starbright XLT fully multicoated optics: This high transmission/high reflectivity optical coatings package applied to each optical surface gives you visibly higher light transmission for brighter deep space images and shorter exposure times during imaging. It also increases the contrast on subtle lunar, planetary, and nebula details when compared with optics using ordinary coatings or multicoatings. For more details, click on the "Starbright XLT" link in the support tab above.

Fastar compatible: For the ultimate in wide-field catadioptric imaging, the EdgeHD optical tube is Fastar compatible to allow CCD imaging at a blazingly-fast f/2 focal ratio. For f/2 imaging, an optional Fastar lens assembly lens replaces the scope's removable secondary mirror (an exchange that takes only a few minutes). Your CCD camera is attached to the Fastar lens. This puts your camera at the f/2 position in the center of the Schmidt corrector lens at the front of the optical tube, rather than in its normal f/10 position at the Cassegrain focus at the rear. The Fastar option is for imaging only and cannot be used for visual observing.

This Celestron Optical Tube's Mechanics . . .

Focusing: Focusing is accomplished by turning a knob on the rear cell that moves the primary mirror fore and aft along the central baffle tube to adjust the focus. The Celestron focusing mechanism is supported by two pre-loaded ball bearings, minimizing the "mirror flop" typical of bushing-type focus mechanisms that causes image shift during critical focusing.

Mirror locks: Flexible tension locks hold the mirror in place after correct focus is achieved for imaging and reduce image shift when rotating the tube around a mount (when moving past the zenith during astrophotography, for example). Unlike other designs that have only one locking knob located off to one side of the mirror, the Celestron system uses three locks equally spaced around the mirror to distribute the mirror locking force symmetrically.

The focuser itself acts as one of the locks, while two flexible rods spaced 120° away in either direction act as the second and third locks. Controlled by variable tension knobs on the rear cell, these rods act in conjunction with the focuser to hold the mirror in place without putting any asymmetrical force or pressure on the mirror. This keeps the image centered in the eyepiece (or chip) no matter what the orientation of the optical tube.

Tube vents: Two cooling vents on the rear cell allow warm air to be released from behind the primary mirror when the scope is taken out for a night's observing or imaging. This shortens the amount of time needed for the optics to cool down to ambient air temperature for peak performance. Each vent has an integrated 60 micron micro-mesh filter guaranteed to let warm air out without letting dust in.

Dovetail rail: The full length dovetail rail mounted under the optical tube fits Celestron CGEM, CGE, and CGE Pro mounts, as well as any other make or model German equatorial mount that uses a Losmandy-style "D-plate" mounting dovetail slot.

This Celestron Optical Tube's Supplied Accessories . . .

Finderscope: The supplied 9 x 50mm straight-through achromatic design finderscope has a wide 5.8 degree field of view. It is mounted in a spring-loaded easy-adjust quick release bracket.

Star diagonal: The supplied star diagonal is a 1.25" prism type. Also included is a 1.25" visual back.

Eyepiece: The standard equipment eyepiece is a 1.25" 40mm Plössl (51x). The eyepiece field of view is 0.84 degrees, almost 70% larger than the full Moon.

Two-year warranty: All Celestron optical tubes have a two-year warranty.