Celestron C11 XLT Optical Tube Assembly OTA CGE

Reference 91036

£2,999.00 VAT inc

Celestron Schmidt-Cassegrain Optical Tube Assemblies (OTA) are available individually for use with your favorite mount

  • 11″ Schmidt-Cassegrain Optical Tube Assembly
  • Aluminum Optical Tube
  • Celestron’s premium StarBright XLT coatings
  • 2800 mm focal length (f/10)
  • 40 mm eyepiece included (70x)
  • Visual back allows for use with 1.25″ accessories
  • 9×50 finderscope to help accurately find objects
  • Star diagonal provides more comfortable viewing position when observing objects that are high in the sky
  • Includes dovetail rail compatible with CGE mount

Delivery In 1-5 Days

Our Description


Optical Design
Aperture (mm)
279.4 mm (11 in)
Focal Length
2800 mm (110 in)
Focal Ratio
Focal Length of Eyepiece 1 (mm)
40 mm (1.57 in)
Magnification of Eyepiece 1
70 x
Star Diagonal
Optical Tube
Highest Useful Magnification
660 x
Lowest Useful Magnification
40 x
Limiting Stellar Magnitude
Resolution (Rayleigh)
0.5 arc seconds
Resolution (Dawes)
0.42 arc seconds
Light Gathering Power (Compared to human eye)
1593 x
Secondary Mirror Obstruction
3.75 in (95 mm)
Secondary Mirror Obstruction by Diameter
34 %
Secondary Mirror Obstruction by Area
12 %
Optical Coatings
StarBright / XLT
Optical Tube Length
24 in (610 mm)
Optical Tube Weight
27.5 lbs (12 kg)

Dovetail Compatibility

CGE Mount

Our view

The largest of the Celestron’s SCT OTAs that can be used successfully on the mid-priced German equatorial mounts available, e.g. Celestron CGEM, Skywatcher EQ6 and EQ6 Pro. The Skywatcher HEQ5 will handle the tube assembly for visual use, but may be a little lightweight for serious imaging. This tube assembly is offered as a complete telescope product on the Advanced GT CG5 mount, however, modern imaging requires suitable mounting for ease of tracking, and the CG5 and EQ5 mount are not recommended by us for the C11 tube assembly because of the weight of the tube.
Suitably mounted, the C11 is an excellent observing instrument for deep-sky and planetary. This is the largest SCT tube assembly that can be considered portable rather than transportable. It can be transported by car to a dark sky site or star party in its foam lined carton, or it will sit up quite happily on the front seat of a car with a seat belt around it (author’s experience). A good quality 2″ star diagonal is a must for this telescope as the use of 2″ 40mm and 35mm eyepieces is very rewarding. The Celestron Luminos 31mm, Baader Scopos 35mm and Skywatcher Aero ED 40mm eyepieces are ideal for this telescope. With an Oxygen III filter, the Veil Nebula in Cgynus is an event in itself (even better in the C14 OTA). The reason (apart from aperture) is the successful baffle system in the SCT plus the XLT coatings, diffuse nebula are simply easier to see in greater contrast now.
The C11 is a successful planetary telescope due to its aperture. A larger aperture means that higher magnifications can be used but this depends on the atmospheric stability in any given site. A popular accessory is a binoviewer, this uses a beam splitting prism, and can provide a more stable image when using two eyepieces and two eyes. For planetary imaging, we only have to visit websites such as www.damianpeach.com to see what can be achieved with Celestron larger aperture SCTs.

Photographically it is a diffraction limited 2800mm f/10 telephoto, a 5600mm f/20 telephoto by adding a 2X Barlow, or a 1764mm f/6.3 telephoto by adding the Celestron f/6.3 focal reducer lens.


Budget for the SCT t-adapter, the f/6.3 focal reducer, a 2″ star diagonal so 2″ eyepieces can be used, a Neutral Density filter or Polariser for the moon, the Celestron dewshield, and the Baader UHC and Oxygen III filters. Don’t under-mount this telescope.

PDF Specification sheet for filters and dew straps


Reference: 91036


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