Telescope Comparison
Sky-Watcher Evostar 80ED + HEQ5 Pro vs William Optics Zenithstar 81
The Sky-Watcher Evostar 80ED + HEQ5 Pro is a complete setup. The William Optics Zenithstar 81 needs a mount before it's usable.
First light
Sky-Watcher · 80mm · £690
The automated deep-sky platform
- 80mm refractor 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
- 22.5kg total — requires a fixed garden spot or car transport
William Optics · 81mm · £699
The custom-rig optical tube
- 81mm refractor — optical tube only, no mount included
- 559mm focal length at f/6.9
- 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
William Optics Zenithstar 81 gathers 1× 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 Evostar 80ED + HEQ5 Pro's longer focal length reaches higher magnification with the same eyepiece — better reach for planetary detail. William Optics Zenithstar 81's shorter focal length gives a wider true field — better for large open clusters and extended nebulae.
Focal ratio
William Optics Zenithstar 81's faster f/6.9 delivers wider fields with any eyepiece — better for open clusters and large nebulae. Sky-Watcher Evostar 80ED + HEQ5 Pro's f/7.5 provides more magnification per eyepiece — better for fine planetary detail.
Mount type
William Optics Zenithstar 81 has no mount — add a compatible mount before you can observe. Sky-Watcher Evostar 80ED + HEQ5 Pro is a complete ready-to-use system.
Weight (OTA)
Similar optical tube weight. Any portability difference between these setups comes from the mount, not the tube itself.
Optical design
Both are refractors — no mirrors to collimate, good contrast, colour-free stars with ED or APO glass. The differences between them are in aperture, focal ratio, and glass quality.
At the eyepiece
Both scopes · same aperture
Both refractors share essentially the same aperture — views through each will be very similar on all standard targets. The hallmarks of good refractor optics are sharp stars and good contrast on planetary targets, with no false colour on ED or apochromatic glass. Saturn's rings are distinct from the disk; Jupiter shows two equatorial bands. The Orion Nebula (M42) is bright and well-defined. Open clusters are a strength — the Double Cluster in Perseus and the Pleiades look good at low power. The differences between these two scopes show up in focal ratio, focal length, and what they're optimised for, not in fundamental light-gathering capability.
The real tradeoff
Both scopes are capable. The question is which one fits the way you actually observe.
The Sky-Watcher Evostar 80ED + HEQ5 Pro is a complete package — everything arrives in one box and you can observe the same day. The William Optics Zenithstar 81 is a bare optical tube that needs a separate compatible mount before you can point it at anything, adding significant cost and complexity. Unless you already own a suitable mount, the Sky-Watcher Evostar 80ED + HEQ5 Pro is the practical choice.
The dark side
Every scope has a personality. Here’s where each one gets difficult.
Sky-Watcher
Sky-Watcher Evostar 80ED + HEQ5 Pro
Alignment required every session
GoTo star alignment cannot be skipped — the mount needs to know where it is pointing before it can find objects. This adds several minutes to the start of every session, every time.
Not a spontaneous telescope
At 22.5kg total, this goes out when you plan to go out — not for a quick look on a clear evening.
William Optics
William Optics Zenithstar 81
No mount included
You cannot observe until you buy a separate compatible mount — add at least £100–300 before you have a working telescope.
Nothing to look through on day one
Until a mount arrives, the optical tube is a piece of glass you cannot point at the sky.
Which is right for you?
Two different buyers. Two different right answers.
The automated deep-sky platform
Sky-Watcher · Sky-Watcher Evostar 80ED + HEQ5 Pro
You’ll love this if…
- You want to navigate straight to targets without a star atlas — align once and the scope slews to any object in its database on demand
- You observe from a light-polluted garden where star-hopping to faint deep-sky objects would take most of a clear night
- Astrophotography is where you're headed — the tracking equatorial mount is the essential first component of any imaging setup
This will frustrate you if…
- You find the star alignment required at the start of every session frustrating — GoTo alignment cannot be skipped, and several minutes on a cold night before you can observe is the reality
- You want to take it out for spontaneous sessions — at this weight, getting it in and out of a car on your own requires planning and ideally a second pair of hands
The custom-rig optical tube
William Optics · William Optics Zenithstar 81
You’ll love this if…
- You already own a compatible equatorial or alt-az mount — this is the optical tube you've specifically chosen to put on it
- You're building an imaging rig piece by piece and know exactly what you need at the end of a focuser
- Choosing an optical tube independently of the mount gives you more flexibility over your overall system
This will frustrate you if…
- You buy it without fully accounting for the mount — add at least £100–300 to the purchase price before you have a working telescope
- You expected a complete package and didn't realise this is a bare optical tube that cannot be used without a separate mount
Our verdict
This comparison has a catch: the William Optics Zenithstar 81 is a bare optical tube. You cannot use it without a separate mount — which adds meaningful cost and complexity. The Sky-Watcher Evostar 80ED + HEQ5 Pro is a complete, ready-to-observe package.
For most buyers, the Sky-Watcher Evostar 80ED + HEQ5 Pro is the right choice — you can observe the same night it arrives. The William Optics Zenithstar 81 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 Evostar 80ED + HEQ5 Pro, without hesitation.
Sky-Watcher Evostar 80ED + HEQ5 Pro
View Sky-Watcher Evostar 80ED + HEQ5 Pro →William Optics Zenithstar 81
View William Optics Zenithstar 81 →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 | Sky-Watcher Evostar 80ED + HEQ5 Pro | William Optics Zenithstar 81 |
|---|---|---|
Apertureⓘ The most important spec — bigger = more light = better views | 80mm | 81mm |
Focal Length Longer = more magnification potential | 600mm | 559mm |
Focal Ratio Lower f-number = wider field of view; higher = more magnification per eyepiece | f/7.5 | f/6.9 |
Optical Design The type of optics — each design has different strengths | Refractor | Refractor |
Coatings Better coatings = more light transmission through the optics | Fully multi-coated ED glass, FMC on all air-to-glass surfaces | Fully multi-coated apochromatic triplet (FPL-53) |
How do you point it?
| Spec | Sky-Watcher Evostar 80ED + HEQ5 Pro | William Optics Zenithstar 81 |
|---|---|---|
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 | Sky-Watcher Evostar 80ED + HEQ5 Pro | William Optics Zenithstar 81 |
|---|---|---|
Focuser Size 2" accepts wider eyepieces and gives better low-power views | 2" | 2" |
Focuser Type Rack-and-pinion is standard; Crayford and dual-speed are smoother | Crayford dual-speed (with 1.25" adapter) | Dual-speed Crayford (10:1) |
Size & weight
| Spec | Sky-Watcher Evostar 80ED + HEQ5 Pro | William Optics Zenithstar 81 |
|---|---|---|
OTA Weightⓘ Optical tube only — useful for comparing mount load capacity | 2.2kg | 1.86kg |
Total Weight Full setup including mount — this is what you lug to the car | 22.5kg | — |
Tube Length | 600mm | 390mm |
Tube Material | Aluminium, white powder coat | Aluminium |
What's in the box?
| Spec | Sky-Watcher Evostar 80ED + HEQ5 Pro | William Optics Zenithstar 81 |
|---|---|---|
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 correct-image finder with illuminated reticle | — |
Diagonal Tilts the eyepiece 90° for comfortable viewing — useful on refractors |
Blue highlight: Sky-Watcher Evostar 80ED + HEQ5 Pro advantage · Amber highlight: William Optics Zenithstar 81 advantage · Greyed cells: equal or subjective.