Telescope Comparison
Sky-Watcher Evostar 100ED vs Vixen ED80Sf
The specs are close. The experience isn't.
First light
Sky-Watcher · 100mm · £449
The custom-rig optical tube
- 100mm refractor — optical tube only, no mount included
- 900mm focal length at f/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
Vixen · 80mm · £649
The custom-rig optical tube
- 80mm refractor — optical tube only, no mount included
- 600mm focal length at f/7.5
- 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 100ED gathers 1.6× 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 100ED's longer focal length reaches higher magnification with the same eyepiece — better reach for planetary detail. Vixen ED80Sf's shorter focal length gives a wider true field — better for large open clusters and extended nebulae.
Focal ratio
Vixen ED80Sf's faster f/7.5 delivers wider fields with any eyepiece — better for open clusters and large nebulae. Sky-Watcher Evostar 100ED's f/9 provides more magnification per eyepiece — better for fine planetary detail.
Mount type
Neither scope includes a mount — both require a separate purchase before you can observe.
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 100ED | Vixen ED80Sf |
|---|---|---|
| Planets | ||
| Moon | Excellent 100mm aperture and f/9 focal ratio reward high magnification with sharp, high-contrast lunar detail | Excellent 80mm aperture with ED glass delivers sharp, colour-free crater detail; f/7.5 handles high magnification well |
| Saturn | Good 900mm focal length and clean ED optics show rings, Cassini Division in good seeing, and subtle disc banding | Good Rings clearly defined, Cassini Division visible in steady seeing; 600mm focal length adequate for useful magnification with a short Barlow |
| Jupiter | Good 100mm resolves two or more cloud belts, GRS, and moon shadow transits; f/9 handles high power well | Good Main equatorial belts and GRS visible; ED glass keeps the limb clean, but 80mm limits fine belt detail |
| Mars | Moderate Disc visible with polar cap and large albedo features at opposition, but 100mm limits fine surface detail | Challenging Small orange disc visible at opposition; polar cap hints possible but aperture too small for surface detail |
Deep sky | ||
| Orion Nebula (M42) | Good Bright nebula core and trapezium well shown, but 900mm focal length crops the outer wings | Excellent 80mm aperture and 600mm focal length frame the full nebula with surrounding structure; trapezium resolved |
| Andromeda Galaxy (M31) | Good Bright core and inner halo visible; 900mm frames only the central region, missing the full extent | Excellent 600mm focal length captures the full extent of the galaxy; bright core and inner dust lanes visible |
| Open clusters | Good Compact clusters like M35 frame well; larger groups like the Double Cluster fill the low-power field | Excellent 600mm focal length gives wide true field — Pleiades, Double Cluster, and M35 all fit beautifully with pinpoint stars |
| Globular clusters | Moderate M13 and M5 appear granular at high power but the core remains unresolved at 100mm | Moderate M13 and M3 appear as fuzzy concentrated balls; 80mm cannot resolve individual stars |
| Faint galaxies | Moderate Brighter Messier galaxies detectable as smudges; 100mm lacks the aperture for structure or faint targets | Moderate Brighter Messier galaxies (M81/M82, M51) visible as faint smudges; no structure detail at 80mm |
| Milky Way / wide field | Not recommended 900mm focal length produces too narrow a field for sweeping Milky Way star fields | Good 600mm is slightly long for sweeping Milky Way fields but still delivers rich star clouds with a wide-field eyepiece |
Other | ||
| Double stars | Excellent Clean ED optics at f/9 produce tight diffraction patterns; Dawes limit around 1.2 arcseconds | Good Clean ED optics split Albireo easily and handle tighter pairs like Castor; Dawes limit ~1.45 arcsec |
The real tradeoff
Both scopes are capable. The question is which one fits the way you actually observe.
Sky-Watcher Evostar 100ED
- You'll spend your observing sessions hunting high magnification — 150–200× on the Moon and planets where the 100mm aperture and f/9 focal length genuinely shine, rewarding you with Saturn's Cassini Division and crisp crater detail that justify the long focal length.
- You'll need to commit to a serious equatorial mount before you can observe at all, as the 4.4 kg tube and 900mm length demand stability that adds £400–800+ to your total outlay.
- You'll excel at planetary and lunar work but resent the narrow 900mm field when you want to sweep the Milky Way or frame nebulae whole — the scope pulls tight crops of large targets rather than showing them in context.
Vixen ED80Sf
- You'll frame entire nebulae and galaxy halos in a single field — M42 with its surrounding glow, Andromeda's inner halo, the Pleiades as a complete jewel box — because the 600mm f/7.5 focal length is optimised for wide-field seeing rather than magnification.
- You'll accept smaller planetary and lunar detail (Mars is essentially off the table) as the fair price for a compact, grab-and-observe refractor that demands a lighter, cheaper mount than the Evostar and rewards versatility over specialisation.
- You'll pair this with a camera and equatorial mount to chase deep-sky nebulae rather than planets, because the f/7.5 speed cuts exposure times compared to the Evostar's f/9, and the shorter tube is mechanically easier to track and focus during imaging.
The dark side
Every scope has a personality. Here’s where each one gets difficult.
Sky-Watcher
Sky-Watcher Evostar 100ED
Sold as OTA only with no mount, diagonal, finder, or eyepieces — you cannot observe until you source and budget for these separately, pushing total system cost well beyond the £449 OTA price.
The 900mm focal length is too long for wide-field deep-sky imaging without a focal reducer, and even with one the f/9 ratio demands significantly longer exposures than dedicated f/5–f/7 astrographs.
ED doublet rather than triplet — residual chromatic aberration remains visible on very bright stars, particularly the Moon and bright planets, though substantially less than an achromatic refractor would show.
Vixen
Vixen ED80Sf
OTA only with no mount, diagonal, finder, or eyepieces included — total system cost to observe is substantially higher than the £649 OTA price alone.
80mm aperture is fundamentally limited for deep-sky observation and planetary detail; globular clusters won't resolve into stars and Mars shows only a small orange disc with hints of polar cap at opposition.
Standard focuser is 1.25" only, restricting your choice of eyepieces and accessories; the f/7.5 field also exhibits noticeable coma and field curvature at camera sensor edges without a dedicated field flattener, adding to imaging system cost.
Which is right for you?
Two different buyers. Two different right answers.
The custom-rig optical tube
Sky-Watcher · Sky-Watcher Evostar 100ED
You're right for the Evostar if you're an intermediate observer with your own equatorial mount (or budget to buy one) and you prioritise razor-sharp lunar and planetary views at high magnification — you'll love the clean ED optics on Saturn's rings and tight double stars, and you're willing to accept a narrow field and longer exposures as the trade-off for optical excellence in those domains.
The custom-rig optical tube
Vixen · Vixen ED80Sf
You're right for the ED80Sf if you want a high-quality, portable refractor that shows you entire nebulae and star fields in one view, or if you're stepping into deep-sky astrophotography and need a fast f/7.5 focal ratio that doesn't demand a heavy mount — you'll accept smaller planetary detail and less aperture because you value wide-field versatility and mechanical simplicity over planetary specialisation.
Our verdict
At £449 versus £649, the Vixen ED80Sf costs 45% more. The extra money buys a more capable mount and better build quality, not larger optics.
For most buyers starting out, the Sky-Watcher Evostar 100ED is the sensible choice — put the savings into a better eyepiece. The Vixen ED80Sf makes sense once you know exactly why you need what it offers. If I had to choose: the Sky-Watcher Evostar 100ED, and spend the difference on a quality eyepiece.
Sky-Watcher Evostar 100ED
View Sky-Watcher Evostar 100ED →Vixen ED80Sf
View Vixen ED80Sf →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 100ED | Vixen ED80Sf |
|---|---|---|
Apertureⓘ The most important spec — bigger = more light = better views | 100mm | 80mm |
Focal Length Longer = more magnification potential | 900mm | 600mm |
Focal Ratio Lower f-number = wider field of view; higher = more magnification per eyepiece | f/9 | f/7.5 |
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 doublet | Fully multi-coated ED doublet on all air-to-glass surfaces |
How do you point it?
| Spec | Sky-Watcher Evostar 100ED | Vixen ED80Sf |
|---|---|---|
Mount Type The mechanical system that holds and moves the telescope | None (OTA only) | 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 100ED | Vixen ED80Sf |
|---|---|---|
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 | Dual-speed Crayford (with 1.25" adapter) | Dual-speed Crayford (with 1.25" adapter) |
Size & weight
| Spec | Sky-Watcher Evostar 100ED | Vixen ED80Sf |
|---|---|---|
OTA Weightⓘ Optical tube only — useful for comparing mount load capacity | 2.6kg | 1.8kg |
Tube Length | 720mm | 528mm |
Tube Material | Aluminium | Aluminium |
What's in the box?
| Spec | Sky-Watcher Evostar 100ED | Vixen ED80Sf |
|---|---|---|
Diagonal Tilts the eyepiece 90° for comfortable viewing — useful on refractors |
Blue highlight: Sky-Watcher Evostar 100ED advantage · Amber highlight: Vixen ED80Sf advantage · Greyed cells: equal or subjective.