About this product
Model: cel_r-a_astrograph_8_ota
Part Number: 91073-CGL
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 colour astronomical CMOS, smaller CCD, and mirrorless cameras. Thanks to its fast focal ratio and patented optical design, you can produce sharp, detailed images and often skip the autoguider entirely. Weighing in at just 17 pounds, it’s easy to transport your 8” RASA to the most remote dark sky locations.
Key Features
- 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 airflow while filtering out dust.
- Internal filter mount – seamlessly accommodates a Light Pollution Imaging Filter into the optical path.
- CGE dovetail mounting rail.
- It 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 brighter and more detailed than seen in much bigger telescopes with the naked eye.
Because shorter exposure times are possible, your equatorial mount won’t need to track accurately 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 various mounts.
Ultra-Stable Focus System
With the 8” RASA launch, 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 unsuitable for DSLR cameras. Instead, it has been optimised for use with cameras that have sensors with a diagonal size of ~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. However, some compromise must be expected at the image periphery. Celestron advises 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.
Motorised Focus
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 several 3rd party programs (e.g. Sequence Generator Pro, Maxim DL, etc).
NOTE: The Celestron RASA is a fast astrograph telescope best suited to experienced astronomers.
Rowe-Ackermann Tour
Specifications
| 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) |
Customer reviews
| Average Rating (5 Reviews): | |
06 March 2024 | Simon
I have been imaging for many years and I took a big decision to sell some gear and raise funds to buy this scope. I actually got an open boxed version which saved me a bit of money, but I can assure everybody that this is the most remarkable instrument I have ever used and I have managed in the last few weeks, to produce some of my best pictures by far. The light gathering power of this instrument is remarkable, and whilst everybody comments on this, to actually see the data coming is really something to behold. I have had no collimation issues, no tilt issues, the focuser holds firm and does not move throughout the entire evening. Everything works! I have used a colour ZWO camera on it and a monochrome equivalent, both the 294 models, and in every case using fast narrowband filters or a duo filter, and even straight RGB, I can see absolutely zero problems and this has turned out to be the best astrophotography decision I have ever made. I really am aghast at how this has worked out for me because problems tend to follow me around in this field, but not today! I have just processed a HOO image of Lower's nebula, and I only did 3.5 hours on it, but the image is equivalent to about 15 hours on my other scope, and it seriously shows. Likewise I took about 30 minutes on Orion's nebula, and the detail is astonishing, picking up all sorts of faint nebulosity in the region. I never thought I would get images like I have produced with the Rasa. And with British skies being like they are and with limited imaging time, this scope seriously makes up for the lack of opportunities. I also purchased the Starizona filter drawer to go with this, and the buckeye adaptor, and everything has gone so well by using these two accessories, in conjunction with the scope. I spent a lot of time making a decision about this and FLO helped me out tremendously, throughout the entire time. 6 stars for the scope and 6 stars for FLO staff! Thank you...
20 September 2021 | Keith
As usual FLO were super efficient and prompt even though I knew the product was on back-order it still arrived in under a wekk. Very impressed with the RASA - first light got some lovely wide angle shots of M31 and NGC7000 very quickly, even under a full moon!
03 September 2020 | Stephen
Having seen some very impressive imaging results on SGL using this scope in conjunction with the latest large format and clean CMOS cameras, I thought this scope would work well for me for widefield imaging under intermittent UK skies and I have not been disappointed. First light on M31 gave an impressive result on just 48 minutes of data. The scope is not very forgiving when the moon is up, the background getting washed out very easily, but there is always NB imaging under these conditions. I think it is great value for money alongside other fast astrographs of similar aperture, thoroughly recommended.
06 June 2020 | David
Firstly, the service from FLO was as good as ever, prompt delivery even during the Pandemic. Secondly, the scope itself. Imaging with the ZWO ASI 071 has been a relation, roughly six times faster than my other scopes, sucks in light like a black hole ( well sort of ). Build quality is superb, the focuser is very easy to use compared to my experiences with crayford focusers, very precise and holds focus well, though I haven't imaged for more than an hour and a half. Handled well by my HEQ5 for unguided subs of 40 seconds so far. I will guide for longer subs. I would recommend the Artesky adapter to enable the fitting of a 2" filter especially if you are using OSCs and don't need to change filters. No sign of tilt, though I am not, and have no pretentions to be, a professional or demand my stars in the corners to be absolutely perfect (though if they are not my eyes can't tell). A dew shield is a good idea even if you use a dew heater. For the quality of the scope and the use it will get (will I ever but my other scopes back on the mount?) the price is amazing. Never had so much fun imaging.. Well done Celestron and FLO.
RASA 8 Initiall impressions 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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