Head to head
Same aperture, same tube diameter, same manufacturer, and almost nothing else in common. One is an f/2.2 astrograph with the camera bolted to the front; the other is an f/10 aplanatic Schmidt-Cassegrain with 2 800 mm of focal length. Choosing between them is not a quality judgement — it is a decision about what you intend to photograph.
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Specifications on this record are compiled from public manufacturer documentation and have not been independently re-verified. Tell us if something is wrong.
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.
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 We do not publish prices, because a price we recorded last month is worse than no price at all.
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.
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 We do not publish prices, because a price we recorded last month is worse than no price at all.
If you photograph large nebulae, the RASA is the right telescope and the EdgeHD is the wrong one. If you photograph small galaxies or planets, that reverses completely. And if you ever want to look through the telescope, only one of them has an eyepiece — the RASA physically cannot be used visually.
These two telescopes do not have a single winner. Choose a purpose and the verdict, the winner, the scores and the order of the specification table all change.
Compare for a purpose
The verdict, the winner, the score and the specification order all change with this choice.
Celestron EdgeHD 11 (OTA) leadsWhat matters for visual →
The RASA places its focal plane inside the tube with a camera occupying it. There is no eyepiece position, no visual back, and no adapter that creates one — it is camera-only by design. The EdgeHD is a capable, if demanding, visual telescope: 279 mm of aperture, excellent optics and a narrow field of view, requiring a mount that costs more than the tube. If any part of your plan involves an eyepiece, this comparison has exactly one candidate.
Derived comparison: Celestron EdgeHD 11 (OTA) leads by 6.4 points. The editorial verdict above takes precedence over the arithmetic.
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.
Visual observing
6.4 / 10
Confidence: medium
Outstanding aperture and image quality, but the weight, cost and separate mount requirement make it a demanding visual choice.
| Factor | Score | Weight |
|---|---|---|
| Aperture | 7.7 | 30% |
| Optical qualityeditorial | 8.5 | 20% |
| Ergonomicseditorial | 5.5 | 15% |
| Portability | 5.1 | 15% |
| Mount usabilitySold without a mount — the mount is a separate purchase and a separate decision. | 2.0 | 10% |
| Valueeditorial | 6.0 | 10% |
Weighted total: 6.4. Read the full methodology.
| Specification | Celestron RASA 11 (OTA) | Celestron EdgeHD 11 (OTA) |
|---|---|---|
| Optics | ||
| Aperture | 279.4 mm (11")Equal | 279.4 mm (11")Equal |
| Aperture sets how much you can see. Nothing else substitutes for it. | ||
| Optical design | Rowe-Ackermann Schmidt Astrograph with four-element corrector | Aplanatic Schmidt-Cassegrain with integral field flattener |
| Central obstruction | 42% | 32%Leads here |
| Focal length | 620 mm (24.4")Depends | 2800 mm (110.2")Depends |
| Neither is better — it decides magnification range, not quality. | ||
| Focal ratio | f/2.2Depends | f/10Depends |
| Focal ratio does not make a telescope brighter visually; aperture and magnification do. | ||
| Telescope type | Rowe-Ackermann Schmidt Astrograph | Schmidt-Cassegrain |
| Resolving power (Dawes, calculated) | 0.42"Equal | 0.42"Equal |
| Imaging compatibility | ||
| Usable visually | No — camera only | YesLeads here |
| Mount and tracking | ||
| Mount included | No — OTA onlyDepends | No — OTA onlyDepends |
| A complete package gets you observing tonight. An OTA lets you choose a better mount, at extra cost. | ||
| GoTo | Depends on your mountDepends | Depends on your mountDepends |
| GoTo finds objects; it does not make them brighter. It is a convenience feature, not a purpose. | ||
| Tracking | Depends on your mount | Depends on your mount |
| Size and weight | ||
| OTA weight | 13.6 kg (30 lb) | 12.7 kg (28 lb)Leads here |
| Tube length | 610 mm (24")Equal | 610 mm (24")Equal |
| Product | ||
| Price band | Flagship | Flagship |
| We publish bands rather than prices, because a price we scraped last month is worse than no price at all. | ||
| Status | Current | Current |
Celestron RASA 11 (OTA) leadsWhat matters for nebulae →
At f/2.2 the RASA accumulates signal on extended nebulosity roughly twenty times faster than the EdgeHD at f/10, and its 620 mm focal length frames targets the EdgeHD could only sample a corner of. The EdgeHD with its 0.7× reducer reaches f/7 and 1 960 mm, which is still slow and still narrow. There is no configuration in which the EdgeHD becomes a competitive wide-field nebula instrument.
Derived comparison: Celestron RASA 11 (OTA) leads by 4.5 points. The editorial verdict above takes precedence over the arithmetic.
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.
Nebula imaging
4.1 / 10
Confidence: high
Even with the 0.7× reducer the system is slow and narrow-field; large nebulae simply do not fit.
| Factor | Score | Weight |
|---|---|---|
| Focal ratio | 1.0 | 25% |
| Corrected field | 7.5 | 20% |
| Image circle | 9.8 | 15% |
| Focal length fit | 0.0 | 15% |
| Mount demand | 0.0 | 10% |
| Imaging workfloweditorial | 6.0 | 10% |
| Valueeditorial | 6.0 | 5% |
Weighted total: 4.1. Read the full methodology.
| Specification | Celestron RASA 11 (OTA) | Celestron EdgeHD 11 (OTA) |
|---|---|---|
| Optics | ||
| Focal ratio | f/2.2Leads here | f/10 |
| A faster system reaches a given signal level on extended targets sooner. | ||
| Focal length | 620 mm (24.4")Leads here | 2800 mm (110.2") |
| Scored on fit to large nebulae (roughly 200-600 mm), not on raw length. | ||
| Aperture | 279.4 mm (11")Depends | 279.4 mm (11")Depends |
| For extended nebulosity, focal ratio and field matter more than raw aperture. | ||
| Optical design | Rowe-Ackermann Schmidt Astrograph with four-element corrector | Aplanatic Schmidt-Cassegrain with integral field flattener |
| Telescope type | Rowe-Ackermann Schmidt Astrograph | Schmidt-Cassegrain |
| Central obstruction | 42% | 32%Leads here |
| Resolving power (Dawes, calculated) | 0.42"Equal | 0.42"Equal |
| Imaging compatibility | ||
| Corrected image circle | 43 mmLeads here | 42 mm |
| Compare against your sensor diagonal: 28.3 mm for APS-C, 43.3 mm for full frame. | ||
| Field correction built in | YesEqual | YesEqual |
| Built-in correction removes a corrector, a spacer stack and a backfocus problem from the optical train. | ||
| Largest sensor supported | Full frameLeads here | APS-C |
| Corrector required for imaging | NoEqual | NoEqual |
| Backfocus | 72 mm | 146 mm |
| Backfocus is a hard constraint, not a preference. Your camera, filter drawer and adapters must add up to it. | ||
| Reducer available | No | Yes (×0.7) |
| Usable visually | No — camera only | Yes |
| Mount and tracking | ||
| Mount included | No — OTA onlyDepends | No — OTA onlyDepends |
| Tracking | Depends on your mount | Depends on your mount |
| GoTo | Depends on your mountDepends | Depends on your mountDepends |
| Size and weight | ||
| OTA weight | 13.6 kg (30 lb) | 12.7 kg (28 lb)Leads here |
| Tube length | 610 mm (24")Equal | 610 mm (24")Equal |
| Product | ||
| Price band | Flagship | Flagship |
| Status | Current | Current |
Celestron EdgeHD 11 (OTA) leadsWhat matters for galaxies →
Galaxies are small. At 2 800 mm the EdgeHD delivers around 0.28 arcseconds per pixel with a typical sensor, giving real structure on targets a few arcminutes across; the RASA at 620 mm gives about 1.25 arcseconds per pixel, which renders the same galaxy as a compact blob regardless of how fast the optics are. Speed cannot buy image scale. The EdgeHD's flat, corrected field across an APS-C sensor makes the whole frame usable rather than just the middle.
Derived comparison: Celestron RASA 11 (OTA) leads by 0.9 points. The editorial verdict above takes precedence over the arithmetic.
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.
Galaxy imaging
6.4 / 10
Confidence: high
Aperture, focal length and a genuinely flat field are all in the right place; the demands it places on the mount are the only thing holding it back.
| Factor | Score | Weight |
|---|---|---|
| Focal length fit | 7.6 | 25% |
| Resolving power | 5.8 | 20% |
| Corrected field | 7.5 | 15% |
| Optical qualityeditorial | 8.5 | 15% |
| Mount demand | 0.0 | 10% |
| Imaging workfloweditorial | 6.0 | 10% |
| Valueeditorial | 6.0 | 5% |
Weighted total: 6.4. Read the full methodology.
| Specification | Celestron RASA 11 (OTA) | Celestron EdgeHD 11 (OTA) |
|---|---|---|
| Optics | ||
| Focal length | 620 mm (24.4") | 2800 mm (110.2")Leads here |
| Scored on fit to small galaxies (roughly 900-2000 mm). | ||
| Aperture | 279.4 mm (11")Equal | 279.4 mm (11")Equal |
| Resolving power (Dawes, calculated) | 0.42"Equal | 0.42"Equal |
| Focal ratio | f/2.2Depends | f/10Depends |
| Optical design | Rowe-Ackermann Schmidt Astrograph with four-element corrector | Aplanatic Schmidt-Cassegrain with integral field flattener |
| Telescope type | Rowe-Ackermann Schmidt Astrograph | Schmidt-Cassegrain |
| Central obstruction | 42% | 32%Leads here |
| Imaging compatibility | ||
| Field correction built in | YesEqual | YesEqual |
| Corrected image circle | 43 mmLeads here | 42 mm |
| Largest sensor supported | Full frameLeads here | APS-C |
| Corrector required for imaging | NoEqual | NoEqual |
| Backfocus | 72 mm | 146 mm |
| Reducer available | No | Yes (×0.7) |
| Usable visually | No — camera only | Yes |
| Mount and tracking | ||
| Tracking | Depends on your mount | Depends on your mount |
| Mount included | No — OTA onlyDepends | No — OTA onlyDepends |
| GoTo | Depends on your mountDepends | Depends on your mountDepends |
| Size and weight | ||
| OTA weight | 13.6 kg (30 lb) | 12.7 kg (28 lb)Leads here |
| Tube length | 610 mm (24")Equal | 610 mm (24")Equal |
| Product | ||
| Price band | Flagship | Flagship |
| Status | Current | Current |
Celestron EdgeHD 11 (OTA) leadsWhat matters for planetary →
Planetary imaging wants the longest practical focal length and a slow beam. The EdgeHD offers 2 800 mm natively and 279 mm of aperture resolving to about 0.42 arcseconds, which is more resolution than most nights of seeing will let you use. The RASA offers 620 mm at f/2.2 with a camera obstructing the aperture, and there is no sensible way to amplify that to a planetary image scale. This is a structural mismatch, not a close comparison.
Derived comparison: Celestron EdgeHD 11 (OTA) leads by 1.7 points. The editorial verdict above takes precedence over the arithmetic.
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.
Planetary imaging
7.7 / 10
Confidence: high
Large aperture and 2 800 mm native focal length make this close to an ideal planetary instrument on nights that cooperate.
| Factor | Score | Weight |
|---|---|---|
| Aperture | 7.7 | 30% |
| Focal length fit | 10.0 | 25% |
| Optical qualityeditorial | 8.5 | 20% |
| Collimation & thermals | 4.0 | 10% |
| TrackingNo mount supplied — tracking quality depends entirely on the mount you pair it with. | 5.0 | 10% |
| Valueeditorial | 6.0 | 5% |
Weighted total: 7.7. Read the full methodology.
| Specification | Celestron RASA 11 (OTA) | Celestron EdgeHD 11 (OTA) |
|---|---|---|
| Optics | ||
| Aperture | 279.4 mm (11")Equal | 279.4 mm (11")Equal |
| Aperture sets the resolution ceiling before seeing takes over. | ||
| Focal length | 620 mm (24.4") | 2800 mm (110.2")Leads here |
| Long native focal length reduces how much amplification you have to add. | ||
| Central obstruction | 42% | 32%Leads here |
| A larger obstruction lowers contrast at high magnification, though aperture usually wins the argument. | ||
| Resolving power (Dawes, calculated) | 0.42"Equal | 0.42"Equal |
| Calculated from aperture. Real nights are usually limited by seeing well before this. | ||
| Focal ratio | f/2.2Depends | f/10Depends |
| Optical design | Rowe-Ackermann Schmidt Astrograph with four-element corrector | Aplanatic Schmidt-Cassegrain with integral field flattener |
| Telescope type | Rowe-Ackermann Schmidt Astrograph | Schmidt-Cassegrain |
| Imaging compatibility | ||
| Corrected image circle | 43 mmLeads here | 42 mm |
| Field correction built in | YesEqual | YesEqual |
| Backfocus | 72 mm | 146 mm |
| Largest sensor supported | Full frameLeads here | APS-C |
| Corrector required for imaging | NoEqual | NoEqual |
| Reducer available | No | Yes (×0.7) |
| Usable visually | No — camera only | Yes |
| Mount and tracking | ||
| Tracking | Depends on your mount | Depends on your mount |
| Mount included | No — OTA onlyDepends | No — OTA onlyDepends |
| GoTo | Depends on your mountDepends | Depends on your mountDepends |
| Size and weight | ||
| OTA weight | 13.6 kg (30 lb) | 12.7 kg (28 lb)Leads here |
| Tube length | 610 mm (24")Equal | 610 mm (24")Equal |
| Product | ||
| Price band | Flagship | Flagship |
| Status | Current | Current |
| Aspect | Celestron RASA 11 (OTA) | Celestron EdgeHD 11 (OTA) |
|---|---|---|
| Relative imaging speed on extended targets | About 20× the EdgeHD at f/2.2Depends | Baseline at f/10Depends |
| Speed only matters for extended objects. For a small galaxy that fills few pixels in the RASA, the EdgeHD's image scale matters far more than its slower beam. | ||
| Image scale with a 3.76 µm sensor | About 1.25 arcsec/pixelDepends | About 0.28 arcsec/pixelDepends |
| Under-sampled for galaxies in the RASA; over-sampled for average seeing in the EdgeHD. Neither number is "better" without a target in mind. | ||
| Camera obstruction of the aperture | Camera sits in the light path at prime focus | None — camera is behind the rear cellLeads here |
| A large camera body on the RASA measurably reduces throughput and can add diffraction artefacts, so compact cameras and thin cabling are strongly preferred. | ||
| Backfocus requirement | 72 mm, with very tight tolerance at f/2.2Depends | 146 mm nativeDepends |
| Both are hard constraints. The RASA's is less forgiving because depth of focus at f/2.2 is a fraction of a millimetre. | ||
Both are 279 mm tubes in a 310 mm shell weighing about 13 kg, and both are orange. That is where the similarity ends. The RASA removes the secondary mirror entirely and puts a four-element corrector and the camera at prime focus; the EdgeHD keeps the secondary and adds a field-flattening group in the baffle tube.
The result is a 4.5× difference in focal length and a 20× difference in imaging speed on extended targets, from the same piece of glass at the front.
Not “which is better” but “how big is what you photograph”.
The camera lives in the beam. That means a compact camera, thin cables routed carefully, and a permanent low-level reduction in throughput and some diffraction structure around bright stars. It also means no eyepiece, ever.
At f/2.2 the depth of focus is measured in tens of microns. Temperature drift over a session will move you out of focus, so an autofocuser with temperature compensation stops being a luxury. Sensor tilt that would be invisible at f/7 produces obviously misshapen corner stars here.
None of this makes the RASA a bad telescope. It makes it a specialist one that punishes casual use.
2 800 mm is a long focal length by any amateur standard. Guiding needs to hold well under an arcsecond RMS, the mount needs to be rated far above 12.7 kg, and flexure anywhere in the imaging train will show up as elongated stars that are maddening to diagnose.
Most EdgeHD 11 owners end up running the 0.7× reducer at 1 960 mm and f/7 most of the time, which is a good deal more forgiving and still gives four times the image scale the RASA can offer.
Own the EdgeHD. It photographs galaxies and planets well, observes visually, and reduces to a workable medium-field configuration. It will never photograph the Veil Nebula properly, but the RASA will never photograph anything else, and it will never let you simply look at Saturn.
If you can own two and already have a long-focal-length instrument, the RASA is the most compelling second telescope on this site.
Required, not included
Worth adding
Required, not included
Worth adding
Sections on optical design, mount demands, sensor compatibility and thermal behaviour are covered in the pair-specific analysis above and on each product page.
Ritchey-ChretienOTA only
The cheapest honest route to real galaxy image scale, provided you accept that collimating a Ritchey-Chretien is a skill you will have to acquire.
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.
Scores are derived from a fixed weighting of measurable specifications plus four declared editorial ratings, applied identically to every telescope on this site. Verdicts are written per pair and per purpose, and they override the arithmetic when the arithmetic misses something. We have not tested these telescopes side by side and do not claim to have.
Read the full methodology · Report an error in this comparison
Last updated · first published