About this product
Part Number: 91073
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.
- Flat field free of optical aberrations like field curvature, coma, astigmatism and chromatic aberration across an entire APS-C sensor.
- NEW Ultra-Stable Focus System – six precision sealed ball bearings virtually eliminate image shift.
- 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.
- CGE dovetail mounting rail.
- Performs over a wider spectral range than most telescopes, from 390-800 nm, so more of the light passing through the astrograph is in sharp focus.
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. 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 Cameras
Unlike the larger RASAs, the 8" model is not suitable for use with DSLR cameras. Instead it has been optimised for use with cameras that have sensors with a diagonal size ~22mm, which gives an image circle of 3.15°. This makes it an excellent choice for use with today's highly popular CMOS deep sky cameras, such as the ASI183 & ASI1600 series from ZWO. Starlight Xpress' compact CCD cameras also work very well. And whilst ~22mm diagonal is optimal the RASA 8 can also be used with larger sensors up to 32mm diagonal, including the APS-C sized sensors used in many mirrorless cameras, though some compromise must be expected at the image periphery. Celestron advise camera bodies should be less than ~100mm / 4" in diameter.
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.
Celestron's newly announced Focuser Motor (available separately) provides precise electronic focus control using a Celestron handset (if using a Celestron mount) or via a PC using the supplied focuser utility software or a number of 3rd party programs (e.g. Sequence Generator Pro, Maxim DL etc).
NOTE: The Celestron RASA is a fast astrograph telescope so best suited to experienced astronomers.
|Optical Design ||Rowe-Ackermann Schmidt |
|Aperture ||203 mm (8") |
|Focal Length ||400 mm (15.74") |
|Focal Ratio ||f/2.0 |
|Back focus from top of threaded collar ||29 mm (1.14") |
|Backfocus from included camera adapters ||25 mm (.98") |
|Central obstruction diameter ||93 mm (3.66") |
|Finderscope ||Not included |
|Light Gathering Power (Compared to human eye) ||843x |
|Optical Coatings ||StarBright XLT |
|Optical Tube Weight ||17 lbs (7.7 kg) |
|Average Rating (1 Review): |RASA 8 Initiall impressions
Monday, 28 October 2019 | Francis
I've had the RASA for a few days now, plus being blessed with a couple of nights fairly clear and near the new moon period so quite dark skies. As usual came double boxed with the trimmings making it easy to get going straight away. Spacing is quite critical and mine sits at 24.78mm giving me clean stars across a 4/3rd's OSC camera sensor. I really can't get over the FoV with this scope. I looked at loads of scope/camera combination simulations but none come near the reality when the image pops up on screen. Being f2 sub frames can be down to a few seconds. I'm shooting at 120 or 180 seconds at present on objects like the Bat nebula (Sh2-129) and North American nebulae (NGC7000). M42 burnt out at these exposures, even 30 seconds was too much for the core. I'm still learning - but enjoying every minute of the process.
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