Rowe-Ackermann Schmidt AstrographCamera onlyOptical tube onlyCelestron
A 279 mm f/2.2 Schmidt astrograph with the camera mounted at prime focus — extraordinarily fast, dedicated entirely to deep-sky imaging, and physically incapable of visual use.
The fastest way to collect deep-sky photons at this aperture, sold to people who must accept that there is no eyepiece and never will be.
Sold as an optical tube only. No mount, tripod or head is included. For imaging in particular, the mount is usually the larger part of the total cost.
Where to buy
Links open at the retailer in a new tab. We do not publish prices, because a price we recorded last month is worse than no price at all.
The same four purposes are scored for every telescope on this site, using the same weights. A telescope that is excellent for one is often poor for another — that is the point.
Visual observing
Not applicable
Celestron RASA 11 (OTA) is a camera-only instrument. There is no eyepiece position, so it cannot be used for visual observing at all — this is a property of the optical design, not a shortcoming to be scored.
Nebula imaging
8.6 / 10
Confidence: high
An extremely fast, flat, full-frame system with large aperture — the tight tolerances and camera obstruction are the only real costs.
| Factor | Score | Weight |
|---|---|---|
| Focal ratio | 9.5 | 25% |
| Corrected field | 9.5 | 20% |
| Image circle | 10.0 | 15% |
| Focal length fit | 9.8 | 15% |
| Mount demand | 5.5 | 10% |
| Imaging workfloweditorial | 5.5 | 10% |
| Valueeditorial | 6.0 | 5% |
Weighted total: 8.6. Read the full methodology.
Galaxy imaging
7.3 / 10
Confidence: high
620 mm gives roughly 1.25 arcseconds per pixel, which under-samples all but the largest galaxies despite the aperture.
| Factor | Score | Weight |
|---|---|---|
| Focal length fit | 7.3 | 25% |
| Resolving power | 7.1 | 20% |
| Corrected field | 9.5 | 15% |
| Optical qualityeditorial | 8.5 | 15% |
| Mount demand | 5.5 | 10% |
| Imaging workfloweditorial | 5.5 | 10% |
| Valueeditorial | 6.0 | 5% |
Weighted total: 7.3. Read the full methodology.
Planetary imaging
6.0 / 10
Confidence: high
f/2.2 and 620 mm are the opposite of what planetary imaging needs, and there is no practical way to amplify to a usable scale.
| Factor | Score | Weight |
|---|---|---|
| Aperture | 7.7 | 30% |
| Focal length fit | 2.3 | 25% |
| Optical qualityeditorial | 8.5 | 20% |
| Collimation & thermals | 5.8 | 10% |
| TrackingNo mount supplied — tracking quality depends entirely on the mount you pair it with. | 5.0 | 10% |
| Valueeditorial | 6.0 | 5% |
Weighted total: 6.0. Read the full methodology.
Scores are relative to every telescope on this site, not absolute quality marks. A 6.5 for galaxy imaging and a 6.5 for visual observing do not mean the same thing. How scoring works.
A Schmidt corrector at the front, a fast spherical primary at the back, and — instead of a secondary mirror sending light out of the rear — a four-element lens group at prime focus, with the camera bolted directly in front of the tube.
That arrangement is what makes f/2.2 possible with a flat, full-frame-covering field. It is also what makes visual observing impossible: the focal plane is inside the tube, facing the primary mirror, with a camera occupying it. There is no configuration, adapter or accessory that changes this.
Not possible. See above. Any recommendation of a RASA for visual use is simply wrong.
This is the entire point of the instrument. 279 mm of aperture at f/2.2 accumulates signal on extended nebulosity at a rate nothing else here approaches. Targets that would need eight nights with a small refractor come together in one.
The discipline required is exacting. At f/2.2 the depth of focus is a fraction of a millimetre, so temperature-compensating focus is close to mandatory across a session. Sensor tilt of a few tens of microns visibly deforms corner stars. And the camera itself sits in the beam: a large-bodied camera with thick cabling obstructs a measurable fraction of the aperture and can produce diffraction spikes, so RASA owners favour compact cameras and thin, carefully routed cables.
620 mm produces about 1.25 arcseconds per pixel with a typical sensor — too coarse for anything but the largest galaxies. The aperture is there, the image scale is not. An EdgeHD or a Ritchey-Chretien is the right instrument for that job.
No. Planetary imaging wants the longest practical focal length and a slow beam; the RASA offers the shortest and the fastest. Amplifying 620 mm to a planetary scale would require roughly 8× and would be pointless.
13.6 kg of tube, 610 mm long and 310 mm across, requiring a mount well beyond that rating. Most owners treat it as an observatory or semi-permanent instrument. Collimation is adjusted at the secondary lens group and is checked rather than routinely reset. The exposed corrector plate needs a dew heater in most climates.
| Aperture | 279.4 mm (11") |
|---|---|
| Focal length | 620 mm (24.4") |
| Focal ratio | f/2.2 |
| Optical design | Rowe-Ackermann Schmidt Astrograph with four-element corrector |
| Type | Rowe-Ackermann Schmidt Astrograph |
| Glass / mirror | Schmidt corrector plate with a four-element rare-earth lens group at prime focus |
| Central obstruction | 42% |
| Resolving power | 0.42"Calculated from aperture (Dawes limit), not a manufacturer figure. |
| Limiting magnitude | ≈ 14.2Estimated from aperture under dark skies. Real skies are usually worse. |
| Corrected image circle | 43 mm |
|---|---|
| Backfocus | 72 mm |
| Field correction built in | Yes |
| Usable visually | No — camera only |
| APS-C sensors | Supported |
| Full-frame sensors | Supported |
| Reducer | None offered |
| Corrector required | No |
| Autoguiding | Recommended |
| Mount included | No — optical tube only |
|---|---|
| Tracking | Depends on your mount |
| GoTo | Depends on your mount |
| Mounting interface | Losmandy-style dovetail |
| OTA weight | 13.6 kg (30 lb) |
|---|---|
| Tube length | 610 mm (24") |
| Tube diameter | 310 mm |
| Longest transport dimension | 700 mm (27.6") |
| Brand | Celestron |
|---|---|
| Model | Rowe-Ackermann Schmidt Astrograph 11 |
| Status | Current |
| Price band | FlagshipWe publish bands, not prices. Check the retailer for the current price. |
| Skill level | advanced |
Editorial notes
We list an accessory as included only when the product record says so explicitly. If a mount, eyepiece, camera, flattener, reducer, corrector, guider or adapter is not listed above, assume it is not in the box.
Schmidt-CassegrainOTA only
A superb long-focal-length instrument that will expose every weakness in your mount, your seeing and your guiding before it shows you what it can do.
Imaging NewtonianOTA only
Enormous imaging aperture for the money, sold to people who underestimate what f/4 and 8.5 kg do to a mount.
Petzval refractorCamera onlyOTA only
A tiny, expensive, almost foolproof wide-field astrograph. You are paying for the fact that nothing about the optical train can go wrong.