Celestron 11" Rowe-Ackermann Schmidt Astrograph (RASA) OTA - 91075

Celestron   ——   SKU: CEL-91075
$4,680.00 CAD
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Product Info

Celestron 11" Rowe-Ackermann Schmidt Astrograph

  • 11-inch f/2.2 optical design with rare-earth glass for images free of false color, coma, and field curvature
  • Flat image field free of optical aberrations across an entire APS-C or a DSLR sensor
  • New Ultra-Stable Focus System – precision bearings virtually eliminate image shift; custom-engineered linear brass focuser bearing reduces image shift, while dual-speed 10:1 FeatherTouch Micro Focus Knob provides the most precise manual focusing
  • Integrated air cooling system –12V DC MagLev fan reduces cooldown time and provides optimal air flow while filtering out dust
  • Internal filter mount – seamlessly accommodates a Light Pollution Imaging Filter into the optical path
  • Common camera adapters (T-thread and M48) included for easy attachment to popular CCD and DSLR cameras
  • CGE dovetail mounting rail
  • Performs over a wider spectral range than most telescopes, from 400-700 nm, so more of the light passing through the astrograph is in sharp focus
  • Wider spectral range means brighter image results with your digital camera

The 11" Rowe-Ackermann Schmidt Astrograph (RASA) from Celestron, is a cost-effective optical system for wide field astroimaging. It offers unprecedented value in aperture, speed, field of view, and optical performance. The RASA design has a convenient external prime-focus image capture location with a flat focal plane, providing small spot sizes to the edge of a wide field. The result is images that are free of optical defects like field curvature, off-axis coma, or astigmatism. RASA 11" has an ample back-focus distance of 55 mm with the included camera adapter, which accommodates a wide variety of imaging sensors.

Some Information About the RASA Technology:

Celestron's 11" Rowe-Ackermann Schmidt Astrograph (RASA’s) optical design is patented. The design consists of a Schmidt corrector, spherical primary mirror, lens group, and optical window. The lens group contains 4 elements and utilizes rare-earth elements. Unlike many telescopes that only perform well over the visible spectrum (400 nm - 700 nm), the 11" RASA’s optics are designed to perform over a wider spectral range, from 400 nm - 700 nm. This allows more of the light emitted from the astronomical object to be sharply focused in the image. Also there will be better spectral matching to silicon array sensors.

With many imaging systems, adding an extra piece of flat glass such as a filter may not affect the optical performance. However, that is not the case with super-fast optical systems like the RASA. Celestron's engineers addressed this concern by designing the RASA with a removeable optical window. This means you can maintain peak optical performance if a filter is added or if a camera has its own optical window. Simply remove the flat window and replace it with a Celestron filter. Celestron offers a Light Pollution Imaging Filter designed specifically for the 11" RASA, which replaces that optical window.

All refractive optical surfaces are coated with StarBright XLT coatings, while the primary mirror uses enhanced aluminum coatings. This maintains high light transmission through the entire optical system. When compared with a “Hyperstar SCT” system, the RASA 11 provides better optical performance and field illumination.

11" Astrograph Scope Description:

Capture spectacular wide-field deep sky images in seconds with Celestron’s new portable astrograph, the 11" Rowe-Ackermann Schmidt Astrograph (RASA). Capturing impressive deep-sky astroimages is easier than ever with Celestron’s new Rowe-Ackermann Schmidt Astrograph with 11 inch aperture, the perfect companion to today’s top DSLR or astronomical CCD cameras. This fast, wide-field f/2.2 system offers two huge advantages over traditional f/10 astroimaging: better apparent tracking and shorter exposures. That means you’ll create better-looking astroimages in a fraction of the time, even without the use of an autoguider.

The 11" RASA is an imaging telescope that delivers a flat field without optical aberrations for razor sharp stars across a wide field of view. This astrograph can capture stunning deep-sky astronomical images without the challenges typically presented by longer focal length instruments at a fraction of the cost of those systems. This 11" version has thoughtfully designed features, including the integrated air-cooling system, internal filter mount, and sturdy CGE dovetail mounting bar.

The Rowe-Ackermann Schmidt Astrograph builds on the legacy of Celestron’s Schmidt Camera, which allowed astrophotographers to produce images on film in the 1970s. In today's world of astroimaging, with CCD sensor sizes as large as film — (or larger), the 11" Schmidt Astrograph offers a 43.3 mm optimized image circle to capture pinpoint stars on the largest imaging chips currently in use by amateur astronomers! Combine this large image circle with a focal length of just 620 mm and you have an instrument suitable for wide-field imaging, creating huge mosaics of the night sky, surveying, and even comet hunting.

As a typical astrograph design, this scope was purely designed for imaging, hence the 11" RASA cannot be used visually. The prime focus focal plane is located near the front aperture of the optical system, so it cannot accommodate a traditional eyepiece. Since it is an F/2.2 optical system, imagers can use shorter exposure times to capture detail in faint objects. With sensitive cameras and the proper “live stacking” software, the 11" RASA can provide an almost real-time observing experience. View images on a computer instantly that are brighter and more detailed than can be seen in much bigger telescopes with the naked eye.

The 11" Rowe-Ackermann Schmidt Astrograph from Celestron features newly designed optics with 4-element rare-earth glass in the flattener system, for images free of false color and aberrations like coma and field curvature. The optical quality and spot size across the entire image circle is unprecedented for an astrograph in this price range—or even that of a much more expensive instrument. The design also provides minimal vignetting for the best wide field images. Advanced features like a custom engineered linear brass focuser bearing and FeatherTouch Micro Focus Knob allow you to make the fine adjustments you need to capture the perfect shot. Meanwhile, a 12V MagLev fan reduces cooldown time and provides optimal airflow through the dust filtered optical tube.

Engineered as a complete astroimaging system, every component of the 11" Rowe-Ackermann Schmidt Astrograph is optimized for peak performance with DSLR and astronomical CCD cameras. Down to the thickness of the glass used in the included fully-multicoated optical window or an optional imaging filter, every component of the system has been taken into careful consideration and designed to work together seamlessly to obtain the images you want to get now!

Because shorter exposure times are possible, your equatorial mount won’t need to accurately track over extended periods. The 11" RASA’s relatively short 620 mm focal length also lessens the demand for equatorial tracking accuracy. In many cases, autoguiding will not be required. Weighing only 43 lb, this optical tube pairs perfectly with a wide variety of mounts. This astrograph OTA will be relatively easy to transport to your favorite dark sky imaging site as well as to use in your own home location.


Optical Design 11" Rowe-Ackermann Schmidt Astrograph (RASA)
Aperture 279 mm (11")
Focal Length 620 mm (24.4")
Focal Ratio f/2.2
Central obstruction diameter 114 mm (4.48") (41% of aperture diameter)
Light Gathering Power (Compared to human eye) 1588x
Resolution (Rayleigh) 0.49 arcsecond
Resolution (Dawes) 0.41 arcsecond
Image Circle 43.3 mm (1.7") Ø, 4.0°
Useable field 52 mm (2.04") Ø, 4.8° only minimal performance loss at edge of FOV
Wavelength range 400 - 700 nm
Spot size < 4.4 μm RMS across FOV
Optical Coatings StarBright XLT
Off-axis Illumination 83% at 21 mm (.82") off-axis
Optical Window 68 mm (2.67") Ø
Back focus with included camera adapter 55 mm (2.16")
Back focus from top of threaded collar 72.8 mm (2.86")
Optical Tube Aluminum
Optical Tube Length 838.2 mm (33")
OPtical Tube Diameter 330.2 mm (13")
Focuser FeatherTouch microfocuser, coarse and fine focus
Finderscope Not included
Optical Tube Weight 43 lb (19.5 kg)
Other Features Ventilation fan, dual dovetail mounting bars, mirror support clutches
Included items 42 mm (1.65") T-thread camera adapter, 48 mm (1.89") camera adapter, fan battery pack
Dovetail CGE Dovetail Bar

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