Telescope Comparison
Sky-Watcher Evostar 80ED + HEQ5 Pro vs William Optics Zenithstar 73
The Sky-Watcher Evostar 80ED + HEQ5 Pro is a complete setup. The William Optics Zenithstar 73 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 · 73mm · £599
The custom-rig optical tube
- 73mm refractor — optical tube only, no mount included
- 430mm focal length at f/5.89
- 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
Sky-Watcher Evostar 80ED + HEQ5 Pro gathers 1.2× 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 73's shorter focal length gives a wider true field — better for large open clusters and extended nebulae.
Focal ratio
William Optics Zenithstar 73's faster f/5.89 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 73 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
| Target | Sky-Watcher Evostar 80ED + HEQ5 Pro | William Optics Zenithstar 73 |
|---|---|---|
| Planets | ||
| Moon | Good 80mm aperture delivers sharp, colour-free craters and terminator detail; f/7.5 limits extreme magnification compared to longer focal length scopes | Moderate 73mm aperture shows good crater and terminator detail, but the short 430mm focal length limits useful magnification before the image softens. |
| Saturn | Moderate Rings clearly visible and disc shows colour, but 600mm focal length keeps the image small — Cassini Division requires excellent seeing and high-power eyepieces | Challenging Rings visible and Titan identifiable, but 73mm aperture and 430mm focal length can't reveal the Cassini Division or subtle banding. |
| Jupiter | Moderate Main equatorial belts visible; 80mm aperture and 600mm focal length limit detail on the Great Red Spot and festoons | Moderate Main equatorial belts visible; 73mm falls between the Good and Moderate tiers, and the short focal length makes it hard to push magnification for finer detail. |
| Mars | Challenging Small orange disc visible at opposition; polar cap glimpsable in ideal conditions but surface albedo features are beyond this aperture | Challenging Small disc visible near opposition with possible hint of polar cap, but 73mm aperture and short focal length offer very limited surface detail. |
Deep sky | ||
| Orion Nebula (M42) | Excellent Wide 600mm field frames the full nebula and Running Man beautifully — bright enough to show structure visually and a superb imaging target | Good Core nebulosity and Trapezium visible; the wide field at 430mm frames the full nebula complex nicely, but aperture is just under the 80mm Excellent threshold. |
| Andromeda Galaxy (M31) | Excellent 600mm focal length captures the full galaxy extent including companion galaxies; one of this scope's signature imaging targets | Excellent 430mm focal length frames the full galaxy with room to spare; visually the core and inner dust lanes are visible from dark skies. |
| Open clusters | Excellent Wide field perfectly frames the Double Cluster, Pleiades, and other large clusters with pin-sharp stars across the field | Excellent Wide true field at 430mm is ideal for the Double Cluster, Pleiades, and other large clusters — they sit beautifully in the field of view. |
| Globular clusters | Challenging 80mm aperture cannot resolve individual stars — M13 and M3 appear as fuzzy, unresolved glows | Challenging 73mm aperture shows M13 and M22 as fuzzy unresolved glows — no star resolution possible at this aperture. |
| Faint galaxies | Moderate Visually limited by 80mm aperture; however, with camera and stacked exposures, many faint galaxies are accessible photographically | Challenging 73mm gathers limited light; only the brightest galaxies like M81/M82 show as faint smudges visually. |
| Milky Way / wide field | Good 600mm focal length is at the long end for sweeping Milky Way fields visually, but on camera the wide field and fast optics capture rich starfields well | Excellent 430mm focal length at f/5.9 delivers sweeping rich star fields — among the best use cases for this scope visually and with a camera. |
Other | ||
| Double stars | Good Clean ED optics split well-separated doubles cleanly; Dawes limit at 80mm is ~1.45 arcsec, so tight pairs are out of reach | Moderate 73mm resolves wide doubles like Albireo easily, but the short focal length and modest aperture limit splitting of closer pairs. |
| Astrophotography (deep sky) | Excellent HEQ5 Pro GoTo mount with tracking, 80mm ED optics at f/7.5 (f/6.3 with reducer), and massive payload headroom make this a benchmark widefield imaging rig | Not recommended No mount or tracking included; the OTA is excellent for deep sky imaging but only when paired with an equatorial tracking mount purchased separately. |
| Astrophotography (planetary) | Challenging 80mm aperture and 600mm focal length produce a small planetary disc — limited detail even with lucky imaging techniques | Challenging 73mm aperture and 430mm focal length produce a very small planetary image scale — a Barlow helps but aperture is the fundamental limit. |
The real tradeoff
Both scopes are capable. The question is which one fits the way you actually observe.
Sky-Watcher Evostar 80ED + HEQ5 Pro
- You'll spend the first ten minutes of every session polar-aligning the HEQ5 Pro and waiting for it to settle—the mount is heavy and demands precision, but once locked in, your unguided exposures will hold frame after frame with the accuracy this combination is known for.
- You own a complete imaging system out of the box: GoTo tracking, a mount rated for 13.6 kg of payload, and the optical quality to fill an APS-C sensor edge-to-edge without distortion—add a camera and guide scope, and you're observing within weeks, not months of scavenging for accessories.
- Your imaging sessions reward patience and investment: multi-minute unguided exposures on nebulae are routine, your guide scope sits comfortably on the mount's dovetail, and you'll spend more time composing shots than worrying about whether your gear can deliver them.
William Optics Zenithstar 73
- You're starting from an OTA and nothing else—no mount, no focuser accessories, no diagonal—so your first imaging session requires sourcing and financing a separate equatorial mount before you can point at a single target.
- Once assembled with a suitable mount, your fast f/5.9 focal ratio rewards you with short exposures even in moderately light-polluted skies, and the compact 73mm tube lets you travel to dark sites without loading down a vehicle or a back.
- Your workflow is leaner and more modular: you choose the mount that fits your budget and portability needs independently, you're not locked into the payload constraints of a prepackaged system, but you'll also spend weeks planning and sourcing parts before your first night of actual observing.
The dark side
Every scope has a personality. Here’s where each one gets difficult.
Sky-Watcher
Sky-Watcher Evostar 80ED + HEQ5 Pro
80mm aperture will disappoint you if you expect planetary detail or faint deep-sky objects—Jupiter's Great Red Spot remains invisible, and globular clusters stay unresolved fuzzy balls no matter how long you look.
The ED doublet isn't a triplet APO, so bright stars at high magnification show slight residual chromatic aberration; for imaging this is negligible, but visually it's a reminder you didn't buy an APO.
A field flattener/reducer isn't included, so your first imaging session will reveal coma and field curvature at the edges unless you spend another £150–200 on the dedicated accessory.
The HEQ5 Pro itself weighs ~10 kg on the head alone plus a sturdy tripod—this is not a grab-and-go setup, and careful polar alignment is non-negotiable every time you observe.
Astrophotography as a hobby requires a camera, guiding software, autoguiding hardware, image stacking software, and filters—the bundle price is only the beginning of the real investment.
William Optics
William Optics Zenithstar 73
Sold as OTA only means no mount, eyepiece, diagonal, or finder—you cannot observe without additional purchases, making the apparent £599 price misleading when a functional imaging rig costs £1200+ after adding a mount.
The dedicated Flat73A field flattener is essential for imaging; without it, stars toward the field edges show noticeable coma and curvature, so the flattener becomes a mandatory accessory rather than an optional upgrade.
As an ED doublet rather than an APO triplet, residual chromatic aberration is visible on very bright stars in high-resolution images, though it remains controlled for the aperture size.
73mm aperture limits both visual planetary observing and deep-sky resolution—galaxies and globular clusters simply don't perform, so this is unequivocally an imaging instrument only.
The 2-inch focuser rack-and-pinion can flex under heavier camera and filter train loads, requiring careful optical tube balancing to avoid focus shift during long exposures.
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're the intermediate observer ready to learn imaging workflows and willing to master polar alignment, autoguiding, and stacking software—you want a complete, well-supported system from day one, you've budgeted for a camera and accessories, and you value the convenience of built-in GoTo tracking and massive payload headroom over maximum portability or lower entry cost. You'll love the Sky-Watcher if you're imaging widefield nebulae from a dark-sky site two or three times a month and you want a setup that doesn't punish you for adding a guide scope, filter wheel, or dew heater.
The custom-rig optical tube
William Optics · William Optics Zenithstar 73
You're a builder and a minimalist who enjoys sourcing parts, choosing your own mount to match your observing style and budget, and who values the compact form factor and fast optics for travel to dark skies or remote imaging sites. This is your scope if you already own or plan to buy a capable equatorial mount separately, you're comfortable with a modular workflow and longer setup time, and your primary goal is wide-field imaging of large emission nebulae and Milky Way fields where the fast f/5.9 ratio and small size outweigh the smaller aperture—but it's not for you if you want a single box that's ready to image out of the moment it arrives.
Our verdict
This comparison has a catch: the William Optics Zenithstar 73 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 73 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 73
View William Optics Zenithstar 73 →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 73 |
|---|---|---|
Apertureⓘ The most important spec — bigger = more light = better views | 80mm | 73mm |
Focal Length Longer = more magnification potential | 600mm | 430mm |
Focal Ratio Lower f-number = wider field of view; higher = more magnification per eyepiece | f/7.5 | f/5.89 |
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 FMC ED doublet on all air-to-glass surfaces |
How do you point it?
| Spec | Sky-Watcher Evostar 80ED + HEQ5 Pro | William Optics Zenithstar 73 |
|---|---|---|
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 73 |
|---|---|---|
Focuser Size 2" accepts wider eyepieces and gives better low-power views | 2" | 2" / 1.25" |
Focuser Type Rack-and-pinion is standard; Crayford and dual-speed are smoother | Crayford dual-speed (with 1.25" adapter) | Dual-speed Crayford 2" (10:1 reduction fine focus) |
Size & weight
| Spec | Sky-Watcher Evostar 80ED + HEQ5 Pro | William Optics Zenithstar 73 |
|---|---|---|
OTA Weightⓘ Optical tube only — useful for comparing mount load capacity | 2.2kg | 1.75kg |
Total Weight Full setup including mount — this is what you lug to the car | 22.5kg | — |
Tube Length | 600mm | 320mm |
Tube Material | Aluminium, white powder coat | Aluminium, anodised blue |
What's in the box?
| Spec | Sky-Watcher Evostar 80ED + HEQ5 Pro | William Optics Zenithstar 73 |
|---|---|---|
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 73 advantage · Greyed cells: equal or subjective.