Telescope Comparison
Unistellar Odyssey vs ZWO Seestar S50
The specs are close. The experience isn't.
First light
Unistellar · 50mm · £799
The app-native deep-sky imager
- 50mm sensor-based smart telescope — no traditional eyepiece
- Connects to a smartphone app; the app selects, slews to, and stacks targets automatically
- Best for: faint deep-sky objects — galaxies, nebulae, star clusters built up over minutes
- Not for direct eyepiece viewing — every view is delivered on a phone or tablet screen
- 4.5kg compact all-in-one unit
ZWO · 50mm · £539
The app-native deep-sky imager
- 50mm sensor-based smart telescope — no traditional eyepiece
- Connects to a smartphone app; the app selects, slews to, and stacks targets automatically
- Best for: faint deep-sky objects — galaxies, nebulae, star clusters built up over minutes
- Not for direct eyepiece viewing — every view is delivered on a phone or tablet screen
- 2.5kg compact all-in-one unit
The full picture
The numbers that separate these two scopes — and what they mean at the eyepiece.
Aperture
Equal light-gathering. Aperture won't settle this comparison — the mount, focal ratio, and observing experience are what differ.
Focal length
ZWO Seestar S50's longer focal length reaches higher magnification with the same eyepiece — better reach for planetary detail. Unistellar Odyssey's shorter focal length gives a wider true field — better for large open clusters and extended nebulae.
Focal ratio
Focal ratio is not meaningful for smart telescope sensor systems — the optics are optimised for the built-in sensor rather than interchangeable eyepieces.
Mount type
Same mount type — setup experience and ergonomics will be similar. Differences lie in build quality and included accessories.
Weight (OTA)
ZWO Seestar S50's optical tube is 2.0kg lighter. Relevant if you plan to use it on multiple mounts or carry the tube to dark-sky sites separately.
Optical design
Both sensor-based smart telescopes — no eyepiece, app-controlled, live stacking. The differences are in sensor size, aperture, and companion software quality.
At the eyepiece
| Target | Unistellar Odyssey | ZWO Seestar S50 |
|---|---|---|
| Planets | ||
| Moon | Moderate 50mm aperture limits resolution; craters and maria visible on-screen but fine detail is soft compared to any mid-size visual scope | Moderate Full disc fits the frame well, but 50mm aperture and 250mm focal length limit crater-level detail compared to even budget visual scopes |
| Saturn | Challenging 200mm focal length produces a very small disc; rings identifiable but no Cassini Division or band detail | Challenging Rings detectable via stacking, but 250mm focal length renders the planet very small on the sensor |
| Jupiter | Challenging Disc and Galilean moons visible, but 50mm aperture and short focal length yield minimal cloud band detail | Challenging Disc and main cloud bands visible after stacking, but limited detail at this aperture and focal length |
| Mars | Not recommended Tiny disc even at opposition — 50mm aperture and 200mm focal length cannot resolve surface features | Not recommended Tiny disc even at opposition — 50mm aperture and 250mm focal length cannot resolve surface features meaningfully |
Deep sky | ||
| Orion Nebula (M42) | Good f/4 speed and stacking reveal colour and nebulosity nicely, though 50mm aperture limits faint outer filaments | Good Fast f/5 optics and 250mm focal length capture the full nebula extent with good colour and structure after stacking; aperture below 80mm limits fainter outer regions |
| Andromeda Galaxy (M31) | Excellent 200mm focal length frames the full extent of the galaxy; stacking reveals core, dust lanes, and companion galaxies | Excellent 250mm focal length frames the full galaxy beautifully; dust lanes emerge within minutes of stacking |
| Open clusters | Excellent 200mm focal length gives a wide field ideal for framing large clusters like the Pleiades and Double Cluster | Excellent Short 250mm focal length provides wide field of view — Pleiades, Double Cluster, and similar targets fit the frame perfectly |
| Globular clusters | Challenging 50mm aperture cannot resolve individual stars; stacking shows a fuzzy glow with brighter core | Challenging 50mm aperture cannot resolve individual stars; globulars appear as fuzzy concentrated patches even with extended stacking |
| Faint galaxies | Challenging Stacking can detect faint targets, but 50mm aperture limits surface detail to soft smudges for most galaxies | Challenging 50mm aperture limits light gathering — small and faint galaxies show cores only, with little structural detail |
| Milky Way / wide field | Excellent 200mm focal length at f/4 is well-suited to sweeping rich star fields and large Milky Way structures | Excellent 250mm at f/5 is ideal for sweeping star fields and large nebula complexes |
Other | ||
| Double stars | Moderate 50mm aperture and screen-based viewing limit resolving power; wide doubles split but close pairs will not separate | Not recommended No eyepiece for visual splitting, and 50mm aperture with 250mm focal length cannot meaningfully resolve close pairs on the sensor |
| Astrophotography (deep sky) | Good GoTo tracking and automated stacking produce colour deep-sky images easily, but 50mm aperture and closed ecosystem limit what experienced imagers can achieve | Good Fully automated GoTo and tracking with integrated camera at f/5; alt-az field rotation limits long integrations, and 50mm aperture caps faint-target performance |
| Astrophotography (planetary) | Challenging 50mm aperture and 200mm focal length produce very small planetary discs with limited detail even with stacking | Challenging 50mm aperture and 250mm focal length produce a very small planetary disc; stacking helps but cannot overcome the resolution limit |
| Solar imaging | Not applicable | Good With the included or optional solar filter, the Seestar captures sunspot detail and solar granulation automatically — a unique feature at this price point |
The real tradeoff
Both scopes are capable. The question is which one fits the way you actually observe.
Unistellar Odyssey
- You'll spend your first observing session learning the Unistellar app's interface and workflow, but once familiar, you're working within a curated ecosystem designed to guide you through each step.
- Your deep-sky targets — the Orion Nebula, Andromeda, open clusters — emerge with genuine colour on your phone screen, but you're entirely dependent on the stacking algorithm to reveal what the 50mm aperture cannot resolve alone.
- You own a closed system: the app decides gain, exposure, and processing, and you cannot access raw data or experiment with third-party tools, but this trade-off means zero configuration headaches before you observe.
ZWO Seestar S50
- You'll set up in under two minutes on any tripod and start imaging immediately — the Seestar requires almost no learning curve, but it also offers almost no manual control if the automatic settings don't suit your target.
- Your observing sessions are faster and lighter: 2.5kg total weight means you grab it and go, and the integrated dual-band filter handles light pollution automatically, but you're still limited to whatever the app's automation decides is correct exposure and gain.
- You're working within the ZWO Seestar app and WiFi connection; if either fails, the telescope is inert, and field rotation from the alt-az mount will eventually limit how long you can profitably stack on a single target.
The dark side
Every scope has a personality. Here’s where each one gets difficult.
Unistellar
Unistellar Odyssey
No eyepiece and no traditional visual observing — everything you see is on a phone or tablet screen, not through glass.
50mm aperture cannot resolve individual stars in globular clusters or recover structure in small or faint galaxies, even after extended stacking.
Planets are severely limited: Saturn appears as a tiny disc with suggestion of rings, Jupiter shows colour but minimal band detail, and resolution will not rival even a basic 70mm refractor used visually.
Integrated lightweight tripod is prone to vibration during long stacks if placed on uneven surfaces or in wind.
Closed ecosystem with limited access to raw data or third-party processing — you work entirely within the Unistellar app.
At £799, it competes directly with the ZWO Seestar S50, which offers similar aperture and automation with a different software approach.
ZWO
ZWO Seestar S50
No eyepiece — this is purely a digital imaging device with no visual observing capability whatsoever.
50mm aperture severely limits resolution on planets, small galaxies, and faint deep-sky targets compared to traditional telescopes or larger-aperture imagers.
No manual control over individual sub-exposures, gain, or calibration frames — the app handles everything automatically with limited user override options.
Entirely dependent on the ZWO Seestar app and WiFi connection; poor app updates or dropped connection render the telescope unusable.
Internal dew heater draws battery power, reducing runtime in cold or humid conditions.
Integrated alt-az mount introduces field rotation during longer stacking sessions, limiting effective total integration time on some targets.
Which is right for you?
Two different buyers. Two different right answers.
The app-native deep-sky imager
Unistellar · Unistellar Odyssey
You'll love the Odyssey if you're a beginner who wants instant, beautiful colour images of nebulae and galaxies straight to your phone without learning astrophotography, or an urban observer who needs light-pollution mitigation built into the workflow and doesn't mind working within a curated app ecosystem. You'll appreciate the SETI Institute citizen-science integration if that appeals to you. This isn't for you if you want visual observing through an eyepiece, detailed planetary views, or control over your imaging settings and raw files.
The app-native deep-sky imager
ZWO · ZWO Seestar S50
You'll love the Seestar S50 if you want the absolute fastest grab-and-go imaging experience — set it up in under two minutes on any tripod, connect your phone, and start stacking — and you don't need manual control over gain, exposure, or calibration. The 2.5kg weight and integrated dual-band filter make it ideal for light-polluted suburban locations where you can image from a garden and pack everything away in minutes. This isn't for you if you want to observe visually, resolve fine planetary detail, image faint small galaxies with structure, or have any control over your acquisition settings and processing.
Our verdict
At £539 versus £799, the Unistellar Odyssey costs 48% more. The extra money buys a more capable mount and better build quality, not larger optics.
For most buyers starting out, the ZWO Seestar S50 is the sensible choice — put the savings into a better eyepiece. The Unistellar Odyssey makes sense once you know exactly why you need what it offers. If I had to choose: the ZWO Seestar S50, and spend the difference on a quality eyepiece.
Unistellar Odyssey
View Unistellar Odyssey →ZWO Seestar S50
View ZWO Seestar S50 →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 | Unistellar Odyssey | ZWO Seestar S50 |
|---|---|---|
Aperture The most important spec — bigger = more light = better views | 50mm | 50mm |
Focal Length Longer = more magnification potential | 200mm | 250mm |
Focal Ratio Lower f-number = wider field of view; higher = more magnification per eyepiece | f/4 | f/5 |
Optical Design The type of optics — each design has different strengths | Smart Telescope | Smart Telescope |
Coatings Better coatings = more light transmission through the optics | Multi-coated optics | Multi-coated ED doublet objective |
How do you point it?
| Spec | Unistellar Odyssey | ZWO Seestar S50 |
|---|---|---|
Mount Type The mechanical system that holds and moves the telescope | Integrated | Integrated |
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 | Unistellar Odyssey | ZWO Seestar S50 |
|---|---|---|
Focuser Size 2" accepts wider eyepieces and gives better low-power views | — | — |
Focuser Type Rack-and-pinion is standard; Crayford and dual-speed are smoother | Motorised electric focuser with auto-focus | Motorised electric focuser (auto-focus via software) |
Size & weight
| Spec | Unistellar Odyssey | ZWO Seestar S50 |
|---|---|---|
OTA Weightⓘ Optical tube only — useful for comparing mount load capacity | 4.5kg | 2.5kg |
Total Weightⓘ Full setup including mount — this is what you lug to the car | 4.5kg | 2.5kg |
Tube Length | — | 270mm |
Tube Material | Aluminium alloy | Aluminium alloy with polycarbonate housing |
What's in the box?
| Spec | Unistellar Odyssey | ZWO Seestar S50 |
|---|---|---|
Diagonal Tilts the eyepiece 90° for comfortable viewing — useful on refractors |
Smart features
| Spec | Unistellar Odyssey | ZWO Seestar S50 |
|---|---|---|
Built-in Camera Records and stacks images automatically — no separate camera needed | ||
App Controlled | ||
WiFi | ||
Battery Included | ||
Sensor | 1/1.8" CMOS | 1/2.8" Sony IMX462 CMOS |
Sensor Resolutionⓘ Higher megapixels captures finer detail | 4MP | 2.1MP |
Blue highlight: Unistellar Odyssey advantage · Amber highlight: ZWO Seestar S50 advantage · Greyed cells: equal or subjective.