Celestron Edge HD 800 /CGE View larger

Celestron Edge HD 800 OTA - Losmandy CGE Dovetail

91030-XLT

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EdgeHD is an aplanatic Schmidt telescope designed to produce aberration-free images across a wide visual and photographic field of view. The optical system was designed to reduce more than just off-axis star coma, but also to give an astrograph quality flat focal plane all the way to the edge of the field of view.

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Data sheet

Optical Design Schmidt Cassegrain
Aperture 8 inch
Focal Length 2032 mm
Focal Ratio F10
Finderscope 9x50
Optical Coatings Starbright XLT Coating
Optical Tube Length 17 inch

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Introducing Celestron's New Aplanatic Schmidt Telescope Design!

  • Visibly Sharper Images

  • Superior Performance

  • Enhanced Mechanical Features

  • Fastar® Compatible

EdgeHD is an aplanatic Schmidt telescope designed to produce aberration-free images across a wide visual and photographic field of view. The optical system was designed to reduce more than just off-axis star coma, but also to give an astrograph quality flat focal plane all the way to the edge of the field of view.
True Astrograph Quality
Many optical designs that advertise themselves as "astrograph" quality actually only produce pinpoint stars across a curved focal plane. While this may be acceptable for visual observing, stars will appear out of focus at the edge when used with a flat chip sensor of a digital camera. EdgeHD optics produce a focal plane more than three-times flatter than a standard Schmidt Cassegrain telescope and dramatically flatter than other competing coma-free designs. This guarantees you visibly sharp stars across some of the largest CCD chips available today.
Improved Performance
Superior edge performance not only creates rounder, more pleasing stars but actually improves the resolution and limiting magnitude when compared to telescopes of equal aperture. Starbright XLT® Coatings coupled with Celestron's StarBright XLT coating group on every surface, EdgeHD optics gives you maximum light throughput across the widest visual and photographic spectrum.
Mechanical Features
In addition to Celestron’s new optimized optical design, the EdgeHD tube has been redesigned to make sure you get the most from your optics each and every night.
Mirror Clutches - Flexible tension clutches hold the mirror in place and reduce image shift when rotating the tube around the mount. The flexible rods allow the mirror to be held in place without putting any force or pressure on the mirror assembly, keeping the image centered in the eyepiece (or chip).
Tube Vents - Cooling vents located on the rear cell allow hot air to be released from behind the primary mirror. Each vent has an integrated 60 micron micro-mesh filter guaranteed to let warm air out without letting dust in.
Fastar Versatility - The EdgeHD is the most versatile imaging scope available today. At its native f/10 you can achieve the image scale necessary to capture the smallest of deep sky objects. With the optional reducer lens (coming soon) you can increase your field of view without sacrificing optical performance. A barlow gives you the added power for high resolution planetary, lunar and solar imaging. And of course all EdgeHD optical tubes are Fastar® compatible for ultra fast f/2 wide field imaging. Each tube has been fitted with a removable secondary mirror and are opto-mechanically aligned on a laser bench to ensure they are axially symmetric in any configuration.
Celestron Schmidt-Cassegrain Optical Tube Assemblies (OTA) are available individually for use with your favorite mount. Each OTA is made to the same exacting standards as those used on all our high quality telescopes. All optical surfaces are coated with Celestron’s high efficiency StarBright® multi-layered coating group. These tube assemblies are equipped with the same dovetail mounting bar used on the CGE and Advanced Series for easy attachment to a variety of popular mounts.
GENERAL FEATURES 
• 8" EdgeHD Optical Tube Assembly
• Aluminum Optical Tube
• Celestron's premium StarBright XLT coatings
• 2032 mm focal length (f/10)
• 40 mm eyepiece included (51x)
• Visual back allows for use with 1.25" accessories
• 9x50 finderscope to help accurately find objects
• Star diagonal provides more comfortable viewing position when observing objects that are high in the sky
• Mirror Support Knobs hold the mirror in place and reduces image shift during imaging.
• Tube vents with integrated 60 micron mesh filter allowing hot air to be released from behind the primary mirror. 
• Fastar Compatible optical tubes are equipped with a removable secondary mirror for fast f/2 ccd imaging
• Includes dovetail rail compatible with CGE mount
SPECIFICATIONS:

OPTICAL DESIGN  : Aplanatic Schmidt 
APERTURE  : 203.2 mm (8 in) 
FOCAL LENGTH  : 2032 mm (80 in) 
FOCAL RATIO  : 10 
FINDERSCOPE  : 9x50 
OPTICAL TUBE  : Aluminum 
EYEPIECE 1  : 40 mm (1.57 in) 
MAGNIFICATION 1  : 51 x 
STAR DIAGONAL  : 1.25 
OPTICAL COATINGS  : StarBright XLT 
SECONDARY MIRROR OBSTRUCTION  : 2.7 in (68.58 mm) 
SECONDARY MIRROR OBSTRUCTION BY AREA  : 11.4 % 
SECONDARY MIRROR OBSTRUCTION BY DIAMETER  : 33.8 %
OPTICAL TUBE LENGTH  : 17 in (431.8 mm) 
OPTICAL TUBE WEIGHT  : 14 lb (6.35 kg) 
DOVETAIL COMPATIBILITY  : CGE Mount

Our view.

An excellent imaging optic. 8” aperture, 2032mm focal length, and coma free with a flat focal plane. The Edge HD telescopes and optical tube assemblies have an optical prescription that works in a similar way to the standard f/10 SCTs but with further corrections. With the standard SCT, the Schmidt plate corrects for lower order spherical aberration and coma is reduced by aspherizing the secondary. There is however, still some residual off-axis coma visible on wide field images. This means that star images outside the diffraction limited field become increasingly comatic toward the field edge, extended detail (galaxies, the moon, nebulae), outside the diffraction limited field become increasingly blurred, and the faintest objects at the edge of the field can be rendered beyond visibility. If we remove the residual coma, this problem largely disappears.  However, we still have aberrations such as field curvature to contend with. Visually, field curvature can be partly dealt with by simply re-focusing the eyepiece, so that the detail at the edge of the field comes into focus. We can’t do this with a flat detector such as a CCD or CMOS chip. The correcting lens group in all the Edge HD scopes removes off-axis coma and is designed to provide a field with no field curvature over an area covering a conventional 35mm full frame detector. So, the result is a flat focal plane aplanat. It may be that Celestron have also corrected for any off-axis astigmatism, in which case we can call the Edge HDs flat focal plane anastigmats, however, Celestron do not suggest that off-axis astigmatism is an aberration they have corrected for, so it is more appropriate to term the Edge HDs as flat focal plane aplanats. 
The secondary can be removed to add the Hyperstar system for the C11 OTA. It is important to note that with the secondary removed, the lens group in the baffle tube that corrects for off-axis coma and gives the flat focal plane, is not used at all. The correcting lens of the Hyperstar unit takes over and creates the corrected field at f/2. In this respect, the Edge HD telescopes offer no real advantage over the standard SCTs as a Fastar telescope. If a Celestron SCT optical tube assembly (whether the Edge HD design or standard SCT design), is chosen for f/2 Hyperstar (Fastar) use only, the standard SCT offers the same performance as the Edge HD.
If your budget permits the Edge HD series of optical tube assemblies, then the 8” Edge is the most compact and portable OTA that can be mounted on the conventional heavy duty mounts such as the Celestron CGEM or the Skywatcher EQ6 Pro, as well as the standard CG5 (Advanced GT), EQ5 (and variants of), plus the HEQ5. It is also the ideal instrument for long range terrestrial photography where high resolution at the field edge is required, (e.g. surveillance, observation).
The two types of 8” Edge HDs are listed above. One has a CGE/Losmandy dovetail rail attached, the other has the CG5/EQ5 dovetail rail attached. 

Requirements. You will need a 12v DC Powertank or 230v AC – 12vDC power supply that is regulated and tip positive.

Warranty: 2 years

Tips.

Budget for a Celestron dew shield, the 1.25” Baader Oxygen III and UHC filters, a Baader polarizer set and the t-adapter for the 8” Edge. Collimation is via the three screws on the front face of the secondary mount. Keep these telescopes collimated correctly for optimum performance.

 PDF Specification sheet for filters and dew straps

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