Telescope Comparison
Celestron RASA 8" vs Sky-Watcher SkyMax 150 Pro + HEQ5
The Sky-Watcher SkyMax 150 Pro + HEQ5 is a complete setup. The Celestron RASA 8" needs a mount before it's usable.
First light
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
Sky-Watcher · 150mm · £999
The automated deep-sky platform
- 150mm maksutov-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
- 24kg total — requires a fixed garden spot or car transport
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
Sky-Watcher SkyMax 150 Pro + HEQ5'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. Sky-Watcher SkyMax 150 Pro + HEQ5's f/12 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. Sky-Watcher SkyMax 150 Pro + HEQ5 is a complete ready-to-use system.
Weight (OTA)
Sky-Watcher SkyMax 150 Pro + HEQ5's optical tube is 1.7kg lighter. Relevant if you plan to use it on multiple mounts or carry the tube to dark-sky sites separately.
Optical design
Celestron RASA 8" is a Schmidt-Cassegrain (mirror and corrector, versatile focal lengths); Sky-Watcher SkyMax 150 Pro + HEQ5 is a Maksutov-Cassegrain (mirror and lens corrector, compact tube). Different optical formulas produce different strengths — reflectors give more aperture per pound; refractors give sharper contrast and require no collimation.
At the eyepiece
| Target | Celestron RASA 8" | Sky-Watcher SkyMax 150 Pro + HEQ5 |
|---|---|---|
| Planets | ||
| Moon | Not recommended Imaging-only instrument with no visual capability; 406mm focal length gives very small lunar image scale even for imaging | Excellent 150mm aperture and f/12 focal ratio deliver exceptional lunar detail — rilles, crater terraces, and shadow play at high magnification |
| Saturn | Not recommended No visual use possible; 406mm focal length produces a tiny planetary disc even with high-resolution cameras | Excellent 150mm aperture and 1800mm focal length clearly show the Cassini Division, disc banding, and shadow of the rings on the globe |
| Jupiter | Not recommended Far too short a focal length for planetary imaging; no visual capability | Excellent Multiple cloud belts, the Great Red Spot, and moon shadow transits are visible; 1800mm focal length gives large image scale |
| Mars | Not recommended Extremely small image scale at 406mm; the scope is fundamentally unsuitable for planetary work | Good 150mm aperture shows polar cap and major dark surface features at opposition; falls short of the 200mm+ needed for Excellent |
Deep sky | ||
| Orion Nebula (M42) | 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 | Good Bright core, trapezium stars, and inner nebulosity are well-resolved, but 1800mm focal length frames only the central region |
| Andromeda Galaxy (M31) | 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 | Moderate 1800mm focal length crops heavily — only the bright nucleus and inner core are visible; outer spiral arms are entirely out of field |
| Open clusters | Excellent Wide field at 406mm perfectly frames large clusters like the Double Cluster and M45 with surrounding nebulosity | Moderate Narrow field restricts most large open clusters; compact clusters like M11 are rewarding but Pleiades or Double Cluster overflow the field |
| Globular clusters | Good 203mm aperture resolves outer stars in imaging; short focal length means globulars appear small but well-exposed | Good 150mm resolves stars at the edges of M13 and M92; the long focal length helps by providing high magnification natively |
| Faint galaxies | 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 | Good 150mm gathers enough light for brighter Messier and some NGC galaxies, though the narrow field makes finding them harder |
| Milky Way / wide field | 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 | Not recommended 1800mm focal length produces far too narrow a field for star-field sweeping — less than 1° even with the longest eyepieces |
Other | ||
| Double stars | Not recommended No visual capability; double star work requires visual observation or very long focal lengths for imaging | Excellent 150mm aperture with f/12 unobstructed optics produces clean, high-contrast Airy discs ideal for splitting tight pairs down to ~0.8 arcseconds |
| Large emission nebulae (Veil, North America, Heart) | 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 | Not applicable |
| Narrowband imaging (Ha, OIII, SII) | Excellent f/2 speed makes narrowband practical in short subs; requires filters rated for fast focal ratios to avoid halos | Not applicable |
| Astrophotography (planetary) | Not applicable | Good 150mm aperture and 1800mm native focal length give large image scale for lucky imaging; HEQ5 tracking keeps targets centred |
| Astrophotography (deep sky) | Not applicable | Moderate HEQ5 provides equatorial tracking but f/12 demands impractically long exposures for faint targets; narrow field limits suitable subjects |
The real tradeoff
Both scopes are capable. The question is which one fits the way you actually observe.
Celestron RASA 8"
- You'll never put your eye to this telescope — your entire experience is on a screen, and your observing sessions are really processing sessions where you watch nebulae bloom into view in 60-second subs that would take 12+ minutes at conventional focal ratios.
- You'll frame the entire Veil Nebula complex or Heart and Soul Nebulae side by side in a single shot, and you'll knock out usable narrowband data on a work night because f/2 makes short Ha and OIII subs actually viable — but you'll spend serious money on fast-optic-compatible filters, because standard ones produce ugly halos.
- You're not buying a telescope — you're buying the optical tube for a system that still needs a mount, guide scope, guide camera, imaging camera, and software, so expect to roughly double the sticker price before you capture your first frame.
- You'll spend the first 30–60 minutes waiting for the sealed Mak tube to cool down, then polar aligning the HEQ5 — but once you're settled in, you'll be rewarded with Jupiter's festoons, the Cassini Division, and lunar rilles that make the wait worthwhile.
- You'll feel the narrow field immediately — the Pleiades won't fit, the Orion Nebula gets cropped to its core, and you'll find yourself gravitating naturally toward planets, the Moon, and tight double stars where 1800mm of focal length is an asset, not a limitation.
- You'll appreciate that this setup arrives as a complete, ready-to-observe system with GoTo and tracking, but you'll quickly discover 24kg of gear on a tripod isn't something you casually carry into the garden — this is a commit-to-the-evening telescope.
The dark side
Every scope has a personality. Here’s where each one gets difficult.
Celestron
Celestron RASA 8"
There is no visual capability at all — no focuser, no eyepiece holder, no way to look through this telescope; if you don't already own a dedicated astronomy camera and understand back-focus requirements, you cannot use this scope.
Collimation and sensor tilt are ruthlessly punished at f/2 — even slight misalignment produces elongated stars at the field edges, and the camera plus cabling at the front of the tube create diffraction spikes and reduce effective aperture.
Standard narrowband and light-pollution filters are incompatible — they produce halos, reflections, and severe gradients at f/2, so budget for a full set of fast-optic-rated filters on top of the already significant system cost.
Sky-Watcher
Sky-Watcher SkyMax 150 Pro + HEQ5
The Maksutov's sealed tube needs 30–60 minutes to thermally equilibrate before high-magnification views stabilise — on short winter evenings, that can eat a meaningful chunk of your session.
The HEQ5 is near its practical payload limit with this OTA plus accessories, so adding a guide scope, camera, and dew heater pushes the mount into territory where tracking performance may degrade.
Deep-sky astrophotography is essentially impractical at f/12 — even with a focal reducer the field remains narrow and exposures are very long, so this is not a viable dual-purpose visual-and-DSO-imaging platform.
Which is right for you?
Two different buyers. Two different right answers.
The custom-rig optical tube
Celestron · Celestron RASA 8"
You already own an equatorial mount, a guide setup, and a cooled astronomy camera, and you're tired of spending four-hour sessions stacking 5-minute subs to get enough signal on faint nebulae. You image from a light-polluted driveway and want narrowband data you can actually collect on a weeknight. You have no interest in looking through an eyepiece — your astronomy happens on a monitor — and you're comfortable spending well beyond the OTA price to build the full imaging chain. If you don't already have that infrastructure, this isn't your next purchase.
The automated deep-sky platform
Sky-Watcher · Sky-Watcher SkyMax 150 Pro + HEQ5
You want to see planets and the Moon in genuine detail — the Cassini Division, Jupiter's cloud belts, lunar rilles — and you value the experience of looking through an eyepiece at something real. You're happy to wait for cool-down and spend time on polar alignment because the payoff is steady, tracked, high-magnification views and a clear path into planetary lucky-imaging with a high-speed camera. You're not chasing faint nebulae or wide Milky Way vistas; if sweeping open clusters and framing entire nebula complexes is what excites you, this telescope's narrow field will frustrate you constantly.
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 Sky-Watcher SkyMax 150 Pro + HEQ5 is a complete, ready-to-observe package.
For most buyers, the Sky-Watcher SkyMax 150 Pro + HEQ5 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 Sky-Watcher SkyMax 150 Pro + HEQ5, without hesitation.
Celestron RASA 8"
View Celestron RASA 8" →Sky-Watcher SkyMax 150 Pro + HEQ5
View Sky-Watcher SkyMax 150 Pro + HEQ5 →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 RASA 8" | Sky-Watcher SkyMax 150 Pro + HEQ5 |
|---|---|---|
Apertureⓘ The most important spec — bigger = more light = better views | 203mm | 150mm |
Focal Length Longer = more magnification potential | 406mm | 1800mm |
Focal Ratio Lower f-number = wider field of view; higher = more magnification per eyepiece | f/2 | f/12 |
Optical Design The type of optics — each design has different strengths | Schmidt-Cassegrain | Maksutov-Cassegrain |
Coatings Better coatings = more light transmission through the optics | Fully multi-coated Rowe-Ackermann Schmidt optics | Fully multi-coated Maksutov-Cassegrain optics |
How do you point it?
| Spec | Celestron RASA 8" | Sky-Watcher SkyMax 150 Pro + HEQ5 |
|---|---|---|
Mount Type The mechanical system that holds and moves the telescope | None (OTA only) | GoTo (Computerised) |
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 RASA 8" | Sky-Watcher SkyMax 150 Pro + HEQ5 |
|---|---|---|
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 | Camera threads directly to rear cell (T-thread) | Rear-cell focuser |
Size & weight
| Spec | Celestron RASA 8" | Sky-Watcher SkyMax 150 Pro + HEQ5 |
|---|---|---|
OTA Weightⓘ Optical tube only — useful for comparing mount load capacity | 5.9kg | 4.2kg |
Total Weight Full setup including mount — this is what you lug to the car | — | 24kg |
Tube Length | 368mm | 480mm |
Tube Material | Aluminium | Aluminium |
What's in the box?
| Spec | Celestron RASA 8" | Sky-Watcher SkyMax 150 Pro + HEQ5 |
|---|---|---|
Eyepieces Included eyepieces — more is better, but quality matters more than quantity | — | 25mm Super eyepiece |
Finder Scope Helps you locate areas of the sky before switching to the main eyepiece | — | 8x50 right-angle finder with illuminated reticle |
Diagonal Tilts the eyepiece 90° for comfortable viewing — useful on refractors |
Blue highlight: Celestron RASA 8" advantage · Amber highlight: Sky-Watcher SkyMax 150 Pro + HEQ5 advantage · Greyed cells: equal or subjective.