Telescope Comparison
Sky-Watcher Evostar 80ED + HEQ5 Pro vs William Optics FluoroStar 91
The Sky-Watcher Evostar 80ED + HEQ5 Pro is a complete setup. The William Optics FluoroStar 91 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 · 91mm · £1,299
The custom-rig optical tube
- 91mm refractor — optical tube only, no mount included
- 537mm focal length at f/5.9
- 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 FluoroStar 91 gathers 1.3× 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 FluoroStar 91's shorter focal length gives a wider true field — better for large open clusters and extended nebulae.
Focal ratio
William Optics FluoroStar 91's faster f/5.9 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 FluoroStar 91 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)
Sky-Watcher Evostar 80ED + HEQ5 Pro's optical tube is 1.0kg lighter. Relevant if you plan to use it on multiple mounts or carry the tube to dark-sky sites separately.
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 FluoroStar 91 |
|---|---|---|
| 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 | Excellent 91mm aperture and fluorite correction deliver sharp, high-contrast lunar detail with no false colour on the limb |
| 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 | Good Ring structure and Cassini Division visible in good seeing, though short focal length requires high-power eyepieces to push magnification |
| Jupiter | Moderate Main equatorial belts visible; 80mm aperture and 600mm focal length limit detail on the Great Red Spot and festoons | Good Main cloud belts and GRS visible; 91mm resolves some detail but the 537mm focal length limits comfortable high-power use |
| Mars | Challenging Small orange disc visible at opposition; polar cap glimpsable in ideal conditions but surface albedo features are beyond this aperture | Challenging Disc visible at opposition with hints of albedo features, but 91mm aperture and short focal length make surface detail very difficult |
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 | Excellent 91mm aperture and 537mm focal length at f/5.9 frame the full nebula complex with bright, detailed nebulosity and resolved Trapezium |
| Andromeda Galaxy (M31) | Excellent 600mm focal length captures the full galaxy extent including companion galaxies; one of this scope's signature imaging targets | Excellent 537mm focal length captures the full extent of M31 including companion galaxies; 91mm aperture shows hints of outer halo structure |
| Open clusters | Excellent Wide field perfectly frames the Double Cluster, Pleiades, and other large clusters with pin-sharp stars across the field | Excellent Wide field at 537mm beautifully frames large clusters like the Double Cluster and Pleiades with tight, colour-free stars |
| Globular clusters | Challenging 80mm aperture cannot resolve individual stars — M13 and M3 appear as fuzzy, unresolved glows | Moderate 91mm shows globulars as granular, concentrated balls — M13 has a bright core but individual stars remain unresolved |
| Faint galaxies | Moderate Visually limited by 80mm aperture; however, with camera and stacked exposures, many faint galaxies are accessible photographically | Challenging 91mm gathers limited light for faint galaxies visually; brighter Messier galaxies visible as faint smudges, but detail is minimal |
| 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 537mm at f/5.9 is ideal for rich Milky Way sweeps — star fields through Cygnus and Sagittarius are stunning |
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 | Good 91mm resolves wide and moderate doubles cleanly with excellent colour correction, though close pairs need very short eyepieces at this focal length |
| 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 — optically superb for deep-sky imaging but requires a separate equatorial mount to realise that potential |
| Astrophotography (planetary) | Challenging 80mm aperture and 600mm focal length produce a small planetary disc — limited detail even with lucky imaging techniques | Moderate 91mm and 537mm focal length are limited for planetary imaging; usable with a 2–3× Barlow on a tracking mount, but aperture constrains resolution |
| Emission nebulae (imaging) | Not applicable | Excellent Fast f/5.9 fluorite triplet excels at narrowband and broadband emission nebula imaging — Heart, Soul, North America, and Veil nebulae are ideal targets with a matched flattener |
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 arrive at the dark sky site with a complete, ready-to-deploy imaging rig — the mount is already on your tripod, the OTA slots in, and you're polar-aligning within minutes of unpacking.
- Your observing session begins with careful polar alignment and waiting for the HEQ5 Pro to settle, but once locked in, you'll achieve unguided exposures of several minutes and guided work of 3–5 minutes with minimal fuss.
- You benefit from the HEQ5 Pro's 13.6 kg payload capacity: adding a guide scope, camera, filter wheel, and dew heater doesn't stress the mount, leaving you room to grow without a hardware upgrade.
William Optics FluoroStar 91
- You're buying the optical engine only — you'll source your own mount, and that choice determines your entire observing experience; a budget mid-range EQ mount transforms this into a portable rig, while a premium GOTO mount locks you into significant additional spend.
- Your first imaging session involves finding a field flattener that matches both the OTA and your sensor, testing it in the field, and only then committing to multi-minute exposures; the fluorite glass rewards this fussiness with pinpoint colour-free stars edge-to-edge.
- You're paying a £400 premium over the Evostar bundle primarily for the fluorite correction that matters most in stacked deep-sky images; visually, the gain over ED glass is subtle enough that the cost difference makes sense only if demanding astrophotography is your real goal.
The dark side
Every scope has a personality. Here’s where each one gets difficult.
Sky-Watcher
Sky-Watcher Evostar 80ED + HEQ5 Pro
The 80mm aperture is a hard limit for planetary observation — Saturn's rings are small, Jupiter shows only main cloud belts, and resolving lunar crater detail demands excellent seeing and high eyepiece magnification.
The ED doublet exhibits slight residual chromatic aberration on bright stars at high magnification, though this is negligible for imaging — visually observant users will notice purple fringing on the Moon's limb under steady seeing.
No field flattener is included, so uncorrected coma and field curvature will elongate stars at the edges of your sensor without purchasing a separate 0.85× reducer/corrector.
The HEQ5 Pro itself weighs ~10 kg in the head plus tripod, making this not truly portable; you'll need to perform careful polar alignment each session rather than leaving it set up between observing nights.
Serious astrophotography requires investment in a dedicated astronomy camera, guiding software, autoguiding hardware, filter wheels, and image stacking software — the bundle price does not include these essentials.
William Optics
William Optics FluoroStar 91
Sold as OTA only with no mount, diagonal, finder, or eyepieces included — your total system cost is substantially higher than the £1299 listing price once you add a matched mount and accessories.
The 91mm aperture cannot compete with 130mm+ refractors or larger reflectors at the same total budget for high-magnification planetary and double-star observation.
The visual performance gain from natural fluorite over quality FPL-53 ED glass is marginal in eyepiece use; you're paying a premium that is justified only if you're stacking long-exposure astrophotography frames where sub-arc-second colour correction matters.
Field curvature requires a properly matched field flattener or reducer for imaging — without one, stars elongate noticeably at the frame edges on larger sensors, reducing your effective field quality.
The short 537mm focal length demands very short focal-length eyepieces or a Barlow to achieve high visual magnification, adding further cost and complexity to visual observing.
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're an intermediate observer ready to learn astrophotography workflows and want a complete, GoTo-guided imaging rig that handles wide nebulae and Milky Way starfields with proven, well-supported hardware. You're comfortable with polar alignment, autoguiding, and image stacking software, and you value the convenience of a ready-to-deploy mount with huge payload headroom for your accessories. This isn't for you if you're chasing high-magnification planetary detail, resolving faint deep-sky objects visually, or want an all-round visual telescope — the 80mm aperture is simply too modest for those goals.
The custom-rig optical tube
William Optics · William Optics FluoroStar 91
You'll love this if you're an experienced imager who has already chosen your mount and understands that fluorite's true power lies in stacked deep-sky astrophotography where edge-to-edge colour correction keeps your data clean and your frame flat. You're willing to invest the time finding the right field flattener and you value the portability of a lightweight OTA paired with a mid-range or premium equatorial mount. This isn't for you if you need a complete, grab-and-go package, if planetary observation is a priority, or if you're budget-conscious — the fluorite premium is only justified if demanding astrophotography is your real goal and you're not starting from scratch with mount and accessories.
Our verdict
This comparison has a catch: the William Optics FluoroStar 91 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 FluoroStar 91 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 FluoroStar 91
View William Optics FluoroStar 91 →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 FluoroStar 91 |
|---|---|---|
Apertureⓘ The most important spec — bigger = more light = better views | 80mm | 91mm |
Focal Length Longer = more magnification potential | 600mm | 537mm |
Focal Ratio Lower f-number = wider field of view; higher = more magnification per eyepiece | f/7.5 | f/5.9 |
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 fluorite triplet on all air-to-glass surfaces |
How do you point it?
| Spec | Sky-Watcher Evostar 80ED + HEQ5 Pro | William Optics FluoroStar 91 |
|---|---|---|
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 FluoroStar 91 |
|---|---|---|
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 FluoroStar 91 |
|---|---|---|
OTA Weightⓘ Optical tube only — useful for comparing mount load capacity | 2.2kg | 3.2kg |
Total Weight Full setup including mount — this is what you lug to the car | 22.5kg | — |
Tube Length | 600mm | 430mm |
Tube Material | Aluminium, white powder coat | Aluminium, anodised |
What's in the box?
| Spec | Sky-Watcher Evostar 80ED + HEQ5 Pro | William Optics FluoroStar 91 |
|---|---|---|
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 FluoroStar 91 advantage · Greyed cells: equal or subjective.