Telescope Comparison
Celestron NexStar 6SE vs Celestron RASA 8"
The Celestron NexStar 6SE is a complete setup. The Celestron RASA 8" needs a mount before it's usable.
First light
Celestron · 150mm · £999
The automated deep-sky platform
- 150mm schmidt-cassegrain on a computerised mount with motorised tracking
- Good for: Moon, planets, bright nebulae, star clusters, and deep-sky objects
- GoTo system finds any object in its database after initial star alignment — no star atlas needed
- Tracking motors keep objects centred as Earth rotates — useful above 100×, essential for photography
- 11.5kg total — requires a fixed garden spot or car transport
Celestron · 203mm · £1,799
The custom-rig optical tube
- 203mm schmidt-cassegrain — optical tube only, no mount included
- 406mm focal length at f/2
- Requires a compatible mount before you can observe anything
- Best for: observers who already own a suitable mount or are building a specific imaging rig
- Not a complete purchase — budget at least £100–300 extra for a mount before observing
The full picture
The numbers that separate these two scopes — and what they mean at the eyepiece.
Aperture
Celestron RASA 8" gathers 1.8× more light. On bright targets — Moon, Saturn, Jupiter — you won't notice. On fainter targets — dim galaxies, faint globular clusters — the gap is real.
Focal length
Celestron NexStar 6SE's longer focal length reaches higher magnification with the same eyepiece — better reach for planetary detail. Celestron RASA 8"'s shorter focal length gives a wider true field — better for large open clusters and extended nebulae.
Focal ratio
Celestron RASA 8"'s faster f/2 delivers wider fields with any eyepiece — better for open clusters and large nebulae. Celestron NexStar 6SE's f/10 provides more magnification per eyepiece — better for fine planetary detail.
Mount type
Celestron RASA 8" has no mount — add a compatible mount before you can observe. Celestron NexStar 6SE is a complete ready-to-use system.
Weight (OTA)
Celestron NexStar 6SE's optical tube is 2.4kg lighter. Relevant if you plan to use it on multiple mounts or carry the tube to dark-sky sites separately.
Optical design
Both Schmidt-Cassegrain designs — versatile, compact, good for planets and deep-sky. Differences come from aperture and mount.
At the eyepiece
| Target | Celestron NexStar 6SE | Celestron RASA 8" |
|---|---|---|
| Planets | ||
| Moon | Excellent 150mm aperture and f/10 focal ratio reward high magnification — craterlets, rilles, and sharp terminator shadows are all accessible | Not recommended Imaging-only instrument with no visual capability; 406mm focal length gives very small lunar image scale even for imaging |
| Saturn | Excellent 150mm and 1500mm focal length put Cassini Division, ring shadow, and disc banding within reach in steady seeing | Not recommended No visual use possible; 406mm focal length produces a tiny planetary disc even with high-resolution cameras |
| Jupiter | Excellent Multiple cloud belts, Great Red Spot, and moon shadow transits visible; 1500mm focal length gives a generously sized disc | Not recommended Far too short a focal length for planetary imaging; no visual capability |
| Mars | Good Polar cap and major dark albedo features visible at opposition; 150mm is below the 200mm threshold for truly detailed Mars observation | Not recommended Extremely small image scale at 406mm; the scope is fundamentally unsuitable for planetary work |
Deep sky | ||
| Orion Nebula (M42) | Good Bright nebulosity and Trapezium are impressive, but the 1500mm focal length crops the full extent of the nebula; f/10 doesn't favour wide-field context | Excellent 203mm aperture at f/2 captures the full nebula and running man in seconds; HDR blending reveals both bright core and faint outer wisps |
| Andromeda Galaxy (M31) | Moderate 1500mm focal length frames only the bright core — the outer halo and full disc extend well beyond the field even with a wide eyepiece | Excellent 406mm focal length frames the entire galaxy including companion galaxies M32 and M110 on an APS-C sensor; f/2 speed reveals outer spiral arms quickly |
| Open clusters | Moderate Larger clusters like the Pleiades and Double Cluster overfill the field; works better on compact clusters like M35 or M11 | Excellent Wide field at 406mm perfectly frames large clusters like the Double Cluster and M45 with surrounding nebulosity |
| Globular clusters | Good M13 and M5 show granular texture with partial star resolution at the edges; 150mm is below the threshold for full resolution across the cluster | Good 203mm aperture resolves outer stars in imaging; short focal length means globulars appear small but well-exposed |
| Faint galaxies | Good 150mm gathers enough light to show structure in brighter galaxies like M51 and M104; fainter targets appear as dim smudges | Good 203mm aperture and f/2 speed reveal faint galaxy groups and tidal streams in modest integration times; small image scale limits detail on individual galaxies |
| Milky Way / wide field | Not recommended 1500mm focal length gives far too narrow a field for sweeping Milky Way views — this scope is the opposite of a wide-field instrument | Excellent 406mm at f/2 is purpose-built for wide-field imaging; captures large Milky Way structures like the Cygnus region in a single frame with extraordinary speed |
Other | ||
| Double stars | Excellent 150mm aperture and f/10 focal ratio produce clean Airy discs — excellent for splitting close pairs and showing colour contrast | Not recommended No visual capability; double star work requires visual observation or very long focal lengths for imaging |
| Astrophotography (deep sky) | Moderate Alt-az GoTo mount causes field rotation limiting exposures to a few seconds; usable for EAA and short-exposure stacking but not long-exposure imaging | Not applicable |
| Astrophotography (planetary) | Good 1500mm focal length and tracking mount suit lucky-imaging with a planetary camera; 150mm aperture gives solid detail but falls short of 200mm+ scopes | Not applicable |
| Large emission nebulae (Veil, North America, Heart) | Not applicable | Excellent The RASA 8's defining use case — f/2 speed with 406mm focal length frames and deeply exposes multi-degree emission nebulae in a fraction of conventional integration times |
| Narrowband imaging (Ha, OIII, SII) | Not applicable | Excellent f/2 speed makes narrowband practical in short subs; requires filters rated for fast focal ratios to avoid halos |
The real tradeoff
Both scopes are capable. The question is which one fits the way you actually observe.
Celestron NexStar 6SE
- You'll carry one compact package outside, spend five minutes aligning the GoTo, wait another 30 minutes for the SCT tube to cool down, and then spend the rest of the evening hopping between Jupiter's cloud belts, Saturn's Cassini Division, and a dozen globular clusters — all without touching the mount again.
- You'll actually look through an eyepiece and see things with your own eyes — the Ring Nebula's perfect smoke ring, the colour split of Albireo, craterlets inside Copernicus — and that immediacy is what keeps you coming back on a work night when you don't want to process data.
- You'll get frustrated by the narrow field of view when you try to frame the Orion Nebula or the Pleiades, and you'll feel the single-arm fork wobble every time you refocus, but for compact targets at high magnification the 6SE punches well above its portability class.
Celestron RASA 8"
- You'll never put your eye to this telescope — your camera sensor is the only 'eyepiece' — but you'll capture the entire Veil Nebula complex in a single frame with 60-second subs that would take 12+ minutes at f/7, transforming a weeknight session into serious data.
- You'll spend as much time on setup precision as on imaging itself: collimation and sensor tilt must be dead-on at f/2, your filters must be fast-optic rated or you'll chase halos all night, and dew will attack that exposed corrector plate the moment humidity climbs.
- You'll need to budget well beyond the £1,799 OTA — add a capable equatorial mount, a dedicated astronomy camera, a guide scope and guide camera, and fast-system narrowband filters, and you're looking at a total system cost north of £4,000 before you capture your first frame.
The dark side
Every scope has a personality. Here’s where each one gets difficult.
Celestron
Celestron NexStar 6SE
The single-arm fork mount transmits every touch as 2–3 seconds of vibration — at 200x on Jupiter, that means you'll lose the view every time you adjust focus.
No 2-inch visual back is included, so your maximum true field is stuck around 0.8° with the stock 1.25-inch 25mm Plössl — even with GoTo pointing the scope for you, that's a tiny keyhole to frame anything extended.
The alt-az GoTo mount causes field rotation during exposures, hard-capping deep-sky astrophotography at a few seconds per sub — this is fundamentally a visual scope, not an imaging platform.
Celestron
Celestron RASA 8"
There is no eyepiece holder, no focuser for visual use, and no way to look through this telescope — if you want to see anything with your own eyes, the RASA 8 literally cannot do it.
Standard narrowband and light-pollution filters produce halos, reflections, and severe gradients at f/2 — you must buy filters specifically designed for fast optical systems, which adds significant cost on top of the OTA.
Collimation and sensor tilt are critical at f/2 in a way they simply aren't on slower scopes — even minor misalignment produces visibly elongated stars at the field edges, and achieving correct back-focus spacing to the RASA corrector is fussy with non-native camera setups.
Which is right for you?
Two different buyers. Two different right answers.
The automated deep-sky platform
Celestron · Celestron NexStar 6SE
You want to look through an eyepiece, see Saturn's rings with your own eyes, and have a GoTo system that lets you tour dozens of targets in an evening without star-hopping at 1500mm focal length. You're an intermediate visual observer — maybe in the suburbs — who values portability and tracking convenience, and you're happy trading wide-field framing for sharp planetary and lunar detail. This isn't for you if you're primarily an astrophotographer, or if you need sweeping views of large nebulae and star fields.
The custom-rig optical tube
Celestron · Celestron RASA 8"
You already own an equatorial mount, a dedicated astronomy camera, and a guiding setup — and you want an astrograph that will let you image the North America Nebula, the full Andromeda Galaxy, or SHO narrowband palettes in a fraction of the time any conventional telescope could manage. You're an experienced astrophotographer who understands back-focus, tilt adjustment, and filter compatibility, and you're ready to invest in the ecosystem this OTA demands. This is absolutely not for you if you want to look through a telescope, if you're just starting out in astronomy, or if you don't already have several thousand pounds of imaging hardware waiting for an optical tube.
Our verdict
This comparison has a catch: the Celestron RASA 8" is a bare optical tube. You cannot use it without a separate mount — which adds meaningful cost and complexity. The Celestron NexStar 6SE is a complete, ready-to-observe package.
For most buyers, the Celestron NexStar 6SE is the right choice — you can observe the same night it arrives. The Celestron RASA 8" makes sense if you already own a compatible mount, or are deliberately building a specific imaging setup piece by piece. If I had to choose for a first telescope: the Celestron NexStar 6SE, without hesitation.
Celestron NexStar 6SE
View Celestron NexStar 6SE →Celestron RASA 8"
View Celestron RASA 8" →Deep field: Full specifications
Every data point, for those who want to go further.
Full specifications
Fields highlighted in blue or amber indicate the better value for that spec. Data is manufacturer-stated and may vary.
How much can it see?
| Spec | Celestron NexStar 6SE | Celestron RASA 8" |
|---|---|---|
Apertureⓘ The most important spec — bigger = more light = better views | 150mm | 203mm |
Focal Length Longer = more magnification potential | 1500mm | 406mm |
Focal Ratio Lower f-number = wider field of view; higher = more magnification per eyepiece | f/10 | f/2 |
Optical Design The type of optics — each design has different strengths | Schmidt-Cassegrain | Schmidt-Cassegrain |
Coatings Better coatings = more light transmission through the optics | StarBright XLT fully multi-coated on all optical surfaces | Fully multi-coated Rowe-Ackermann Schmidt optics |
How do you point it?
| Spec | Celestron NexStar 6SE | Celestron RASA 8" |
|---|---|---|
Mount Type The mechanical system that holds and moves the telescope | GoTo (Computerised) | None (OTA only) |
GoToⓘ Computer-controlled pointing — finds any of thousands of objects automatically | ||
Trackingⓘ Motor keeps objects centred as the Earth rotates — essential for astrophotography |
The focuser
| Spec | Celestron NexStar 6SE | Celestron RASA 8" |
|---|---|---|
Focuser Size 2" accepts wider eyepieces and gives better low-power views | 1.25" | — |
Focuser Type Rack-and-pinion is standard; Crayford and dual-speed are smoother | SCT rear-cell focuser | Camera threads directly to rear cell (T-thread) |
Size & weight
| Spec | Celestron NexStar 6SE | Celestron RASA 8" |
|---|---|---|
OTA Weightⓘ Optical tube only — useful for comparing mount load capacity | 3.5kg | 5.9kg |
Total Weight Full setup including mount — this is what you lug to the car | 11.5kg | — |
Tube Length | 394mm | 368mm |
Tube Material | Aluminium | Aluminium |
What's in the box?
| Spec | Celestron NexStar 6SE | Celestron RASA 8" |
|---|---|---|
Eyepieces Included eyepieces — more is better, but quality matters more than quantity | 25mm Plössl | — |
Finder Scope Helps you locate areas of the sky before switching to the main eyepiece | StarPointer red dot finder | — |
Diagonal Tilts the eyepiece 90° for comfortable viewing — useful on refractors |
Blue highlight: Celestron NexStar 6SE advantage · Amber highlight: Celestron RASA 8" advantage · Greyed cells: equal or subjective.