Capture spectacular wide-field deep sky images in seconds with
Celestron’s new portable astrograph, the 8” Rowe-Ackermann Schmidt
Astrograph (RASA). This incredibly fast f/2.0 system is the perfect
companion to today’s color astronomical CMOS cameras, smaller CCD
cameras, and mirrorless cameras. Thanks to its fast focal ratio and
patented optical design, you can produce sharp, detailed images and, in
many cases, skip the autoguider completely. Weighing in at just 17
pounds, it’s easy to transport your 8” RASA to the most remote dark sky
locations.
RASA Performance Made for Everyone
The 8” RASA is an imaging telescope that delivers a flat field
without optical aberrations for razor sharp stars across a wide field of
view. It 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.
The latest addition to the RASA family, this 8” version is a much
more portable and affordable version of the heralded RASA 11, which was
introduced to much acclaim in 2014. With the 8” RASA joining the lineup,
a wider range of astroimagers can enjoy the benefits of the RASA
design. It has many of the same thoughtfully designed features as its
“big brother” RASA 11, including the integrated air-cooling system,
internal filter mount, and sturdy CGE dovetail mounting bar.
Purely designed for imaging, the 8” RASA cannot be used visually. The
prime focus focal plane is located at the front of the optical system,
so it cannot accommodate a traditional eyepiece.
Shorter Exposure Times and Virtual “Real-Time” Observing
Since it is an F/2.0 optical system, imagers can use shorter exposure
times to capture detail in faint objects. When combined with sensitive
cameras and the proper “live stacking” software, the 8” 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.
Because shorter exposure times are possible, your equatorial mount
won’t need to accurately track over extended periods. The 8” RASA’s
relatively short 400mm focal length also lessens equatorial tracking
demands. In many cases, autoguiding will not be required. Weighing only
17 lb, this optical tube pairs perfectly with a wide variety of mounts.
Ultra-Stable Focus System
With the launch of the 8” RASA, Celestron is unveiling a new focuser
design that mitigates lateral movement of the primary mirror when
focusing, slewing, or tracking with the astrograph. Focusing is easier,
more accurate, and more stable than ever. The key to the Ultra-Stable
Focus System is two sets of precision bearings that are precisely
aligned and tested during assembly to ensure optimal results.
Built for Today’s Latest Cameras
Unlike the larger RASAs that work with DSLR and large CCD cameras,
the 8” model was designed with color astronomical CMOS cameras, smaller
CCD cameras, and mirrorless cameras in mind. The telescope does not work
with standard DSLR cameras. It is optimized for sensors with up to a
22mm diagonal, but performs well with sensors up to 32mm diagonal. The
APS-C sized sensors used in many mirrorless cameras are a good choice.
42mm full frame sensors will also work, but performance will be poor at
the edges of the sensor and field illumination will be reduced.
Additionally, we do not recommend pairing RASA 8 with any camera body
more than 4” in diameter. See the chart below to determine if your
camera is compatible with RASA 8.
| Specifications |
|
|---|
| Optical Design | Rowe-Ackermann Schmidt Astrograph |
| Aperture | 203mm (8") |
| Focal Length | 400mm (15.74") |
| Focal Ratio | f/2.0 |
| Central obstruction diameter | 93mm (3.66") (46% of aperture diameter) |
| Light Gathering Power (Compared to human eye) | 843x |
| Resolution (Rayleigh) | 0.68 arc seconds |
| Resolution (Dawes) | 0.57 arc seconds |
| Image Circle | 22mm (.86") Ø, 3.15° |
| Useable field | 32mm (1.26") Ø, 4.6°, only minimal performance loss at edge of FOV |
| Wavelength range | 390 - 800 nm |
| Spot size | < 4.6 µm RMS across image circle |
| Optical Coatings | StarBright XLT |
| Off-axis Illumination | 93% at 11mm (.43") off-axis |
| Optical Window | 46mm (1.81") Ø |
| Back focus with included camera adapter | 25mm (.98") |
| Back focus from top of threaded collar | 29mm (1.14") |
| Optical Tube | Aluminum |
| Optical Tube Length | 628mm (24.7") length | 235mm (9.3") diameter |
| Focuser | Ultra-Stable Focusing System |
| Finderscope | Not included |
| Optical Tube Weight | 17 lbs (7.7 kg) |
| Other Features | Air-cooling system, integrated filter mount |
| Included items | M42 camera adapter, C-thread camera adapter, fan battery pack |
| Dovetail | CGE Dovetail Bar |
In the Box
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