Celestron C8-A XLT Optical Tube Assemblies
Back in the 1970s Celestron made its mark on the astronomy market with the release of its legendary C8 – 8″ Schmidt Cassegrain. Its introduction saw, for the first time, a large aperture, compact telescope design with superior optical quality at an accessible price. To this day the Celestron C8 Schmidt Cassegrain remains a popular choice because of its excellent versatility.
This 8” f/10 optical tube assembly is a descendant of the original revolutionary Celestron C8 – there have been enhancements over the years such as the development of Celestron’s StarBright XLT coatings.
Starbright XLT multicoatings are now standard on all Celestron SCT optical tube assemblies. The process involves the application of:
- high reflectivity multilayer aluminum on the primary mirror
- titanium dioxide overcoated primary mirror for durability
- a unique combination of magnesium fluoride and hafnium dioxide antireflection coatings on both sides of the Schmidt corrector plate.
Together with the use of high transmission water white float glass in the corrector plate the result is markedly improved light transmission.
The benefit of Starbright XLT multicoatings is a visible increase in contrast of subtle details when compared with telescopes using standard multicoatings. The higher light transmission also provides brighter images of faint deep sky targets Across the total visual/photographic spectrum, independent laboratory tests show the new Starbright XLT coatings are 16% brighter overall than previous StarBright coatings.
The Celestron C8 optical tube comes with a 6 x 30mm straight-through achromatic finderscope and mounting bracket. The finder has a wide 7° field of view. Also included is a removable 1.25” visual back, 1.25” prism star diagonal and a 25mm Plössl (1.25”) eyepiece. This eyepiece provides a magnification of 81x, with a field of view just over half a degree – a bit wider than the full Moon’s diameter.
|Aperture (mm)||203.2 mm (8 in)|
|Focal Length||2032 mm|
|Focal Length of Eyepiece (mm)||25|
|Magnification of Eyepiece||81 x|
|Highest Useful Magnification||480 x|
|Lowest Useful Magnification||29 x|
|Limiting Stellar Magnitude||14|
|Resolution (Dawes)||0.57 arc seconds|
|Light Gathering Power (Compared to human eye)||843|
|Secondary Mirror Obstruction||64 mm|
|Secondary Mirror Obstruction by Diameter||31%|
|Secondary Mirror Obstruction by Area||9.77%|
|Optical Coatings||StarBright XLT|
|Optical Tube Length||432 mm|
|Optical Tube Weight||5.7 kg|
Celestron C8-A XLT Schmidt Cassegrain (CG-5)
Part Number: 91020-XLT
Celestron C8-A XLT Schmidt Cassegrain OTA (CGE)
Part Number: 91024-XLT
Choosing between the CG-5 and CGE Dovetail Bars
The Celestron C8-A XLT Schmidt Cassegrain tube assemblies are available with 2 different dovetail plates. You can select either Celestron C8-A XLT (CG-5 bar) or Celestron C8-A XLT (CGE bar). Choose the appropriate model according to the mount you intend to use.
CG-5 bar (narrow or Vixen style dovetail)
The CG-5 (narrow) dovetail plate has a profile 44mm wide at its base. It fits Celestron mounts including the CG-5, Advanced Series Go-To, Advanved VX and newer CGX* German equatorial mounts. It is also compatible with SkyWatcher EQ5, HEQ5, NEQ6 Pro*, EQ6R Pro* and AZ-EQ6* mounts. Losmandy GM8* and G11*. Plus many mounts manufactured by Orion, Vixen and iOptron (mounts marked with an * have dual dovetail saddles that accept either narrow or wide dovetail plates).
CGE bar (wide or Losmandy D-Style)
The CGE (wide) dovetail plate has a profile 75mm wide at its base. It fits Celestron mounts including the CGE, CGE Pro, CGEM, and newer CGX and CGX-L German equatorial mounts. It is also compatible with SkyWatcher NEQ6 Pro, EQ6R Pro, AZ-EQ6 and EQ8 mounts. Losmandy GM8 and G11, Software Bisque Paramount MyT, MX+ and MEII plus many other mounts.
If your mount accepts the wider CGE style bars it is the preferred choice. The wider profile CGE bar provides a more rigid connection between your telescope and mount compared to the CG-5 dovetail.