The new Celestron 8-inch Rowe-Ackermann Schmidt Astrograph
Celestron last year introduced a fast f/2.2 11" RASA Astrograph, and this year follows that up with the new 8" f/2.0 RASA, a high performance Astrograph for $1699. (They are also making the larger 36mm / 14" RASA available to the public after filling initial institutional orders.)
The 8" RASA is an exciting product for astro-imagers - basically a hyperstar system with a 22mm flat field imaging circle, expanding to 32mm. This means it will work for mirrorless APS-C cameras (adapters are available for Canon EOS-M and Sony Mirrorless cameras) but is optimized for astronomical cameras. (Full-frame imagers will want to step up to the big brother 11" RASA.)
Having a focal length of just 400mm, the 8" RASA can be put to use as an exceptional wide field telescope, able to take in the whole of the Andromeda galaxy, Pleiades cluster, and more.
The dedicated light pollution filter is designed to help under even dark skies to eliminate extra skyglow while maintaining color balance.
A Video Astronomy Power-House
The 8" RASA seems ideal for high-end video astronomy, with a C-mount adapter included. This can be great for educational activities.
The 8" RASA is available as a bare OTA, or bundled with the CGEM II or CGX mounts.
Expected availability is November. These will be in high demand, so get your order in early!
Dedicated accessories for the 8" RASA
8" RASA Features
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. It is optimized for sensors with up to a 22mm diagonal, but still performs well with larger (up to 32mm diagonal) sensors. As such, it works well with APS-C sized sensors used in many mirrorless cameras.
Camera adapters to connect C-mount cameras and cameras which mount with M42 threads are included. Celestron offers optional adapters to connect your 8” RASA to Sony or Canon mirrorless cameras.
|Optical Design||Rowe-Ackermann Schmidt Astrograph|
|Aperture||203 mm (8")|
|Focal Length||400 mm (15.74")|
|Central obstruction diameter||93 mm (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||22 mm (.86") Ø, 3.15°|
|Useable field||32 mm (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 11 mm (.43") off-axis|
|Optical Window||46 mm (1.81") Ø|
|Back focus with included camera adapter||25 mm (.98")|
|Back focus from top of threaded collar||29 mm (1.14")|
|Optical Tube Length||628 mm (24.7") length, 235 mm (9.3") diameter|
|Focuser||Ultra-Stable Focusing System|
|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|