Telescope Comparison
Vixen ED80Sf vs William Optics Zenithstar 73
The specs are close. The experience isn't.
First light
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
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
Vixen ED80Sf 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
Vixen ED80Sf'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. Vixen ED80Sf's f/7.5 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 | Vixen ED80Sf | William Optics Zenithstar 73 |
|---|---|---|
| Planets | ||
| Moon | Excellent 80mm aperture with ED glass delivers sharp, colour-free crater detail; f/7.5 handles high magnification well | Moderate 73mm aperture shows good crater and terminator detail, but the short 430mm focal length limits useful magnification before the image softens. |
| Saturn | Good Rings clearly defined, Cassini Division visible in steady seeing; 600mm focal length adequate for useful magnification with a short Barlow | Challenging Rings visible and Titan identifiable, but 73mm aperture and 430mm focal length can't reveal the Cassini Division or subtle banding. |
| Jupiter | Good Main equatorial belts and GRS visible; ED glass keeps the limb clean, but 80mm limits fine belt detail | 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 hints possible but aperture too small for surface detail | 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 80mm aperture and 600mm focal length frame the full nebula with surrounding structure; trapezium resolved | 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 extent of the galaxy; bright core and inner dust lanes visible | 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 600mm focal length gives wide true field — Pleiades, Double Cluster, and M35 all fit beautifully with pinpoint stars | 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 | Moderate M13 and M3 appear as fuzzy concentrated balls; 80mm cannot resolve individual stars | Challenging 73mm aperture shows M13 and M22 as fuzzy unresolved glows — no star resolution possible at this aperture. |
| Faint galaxies | Moderate Brighter Messier galaxies (M81/M82, M51) visible as faint smudges; no structure detail at 80mm | Challenging 73mm gathers limited light; only the brightest galaxies like M81/M82 show as faint smudges visually. |
| Milky Way / wide field | Good 600mm is slightly long for sweeping Milky Way fields but still delivers rich star clouds with a wide-field eyepiece | 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 Albireo easily and handle tighter pairs like Castor; Dawes limit ~1.45 arcsec | Moderate 73mm resolves wide doubles like Albireo easily, but the short focal length and modest aperture limit splitting of closer pairs. |
| Astrophotography (deep sky) | Not applicable | 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) | Not applicable | 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.
Vixen ED80Sf
- You'll spend your observing sessions enjoying planetary and lunar work — Saturn's Cassini Division, Jupiter's belts, and crisp lunar rilles all benefit from the longer 600mm focal length and extra 7mm of aperture.
- Your wide-field visual sweeping will reward you with tight, round stars across the entire field and colour-clean views of M42, Andromeda's halo, and jewel-box open clusters without the violet fringing that cheaper refractors produce.
- Once you add an equatorial mount, your deep-sky imaging becomes a serious possibility; the f/7.5 focal ratio and ED glass work together to deliver well-corrected stars across an APS-C sensor with a field flattener, making nebulae like the Rosette and North America satisfying targets.
William Optics Zenithstar 73
- You'll build your observing around wide-field imaging — the 430mm focal length frames the entire Orion complex, Heart and Soul Nebulae side by side, or all of Andromeda in a single frame, a capability the Vixen cannot match.
- Your visual observing will be functional but limited; you'll see Saturn's rings and Jupiter's belts clearly enough, but the short focal length and modest aperture mean you won't resolve fine planetary detail or faint deep-sky objects that the Vixen's extra aperture reveals.
- The faster f/5.9 ratio keeps exposure times short during imaging, forgiving of mount tracking errors and productive even from light-polluted suburbs when paired with narrowband filters — a speed advantage the Vixen's f/7.5 design cannot exploit as effectively.
The dark side
Every scope has a personality. Here’s where each one gets difficult.
Vixen
Vixen ED80Sf
Sold as OTA only with no mount, diagonal, finder, or eyepieces — your true cost of ownership is £649 plus £400–1500+ for a suitable equatorial mount, making the advertised price misleading.
80mm aperture cannot resolve globular clusters into stars or reveal faint galaxy structure, leaving you visually limited to brighter deep-sky targets compared to 100mm+ scopes at similar total cost.
The 1.25-inch focuser limits your eyepiece and accessory options, particularly if you want to use 2-inch premium oculars common in higher-end observing.
Without a dedicated field flattener, coma and field curvature will degrade star shapes at the edges of APS-C sensor imaging, requiring an additional accessory investment.
William Optics
William Optics Zenithstar 73
Sold as OTA only with no mount, diagonal, finder, or eyepiece included — your total system cost is £599 plus £400–1500+ for a proper equatorial mount, a significant hidden expense.
The Flat73A field flattener is essentially mandatory for imaging; without it, noticeable coma and star curvature appear at field edges, making this accessory a required purchase rather than an optional upgrade.
73mm aperture is insufficient for visual planetary and deep-sky observing — faint galaxies appear as dim smudges and globular clusters won't resolve into stars, limiting this scope's usefulness without a camera attached.
The 2-inch focuser rack-and-pinion can exhibit minor flexure under heavier camera and filter train loads, requiring careful balancing to avoid focus shift during long imaging sessions.
Which is right for you?
Two different buyers. Two different right answers.
The custom-rig optical tube
Vixen · Vixen ED80Sf
You'll love the Vixen ED80Sf if you're an intermediate observer who wants balanced performance across visual observing and astrophotography without sacrifice — you enjoy planetary and lunar detail, wide-field sweeping with sharp stars and colour-clean optics, and you're ready to commit to an equatorial mount to unlock deep-sky imaging. You value the precision engineering and ED glass that minimizes chromatic aberration on bright objects, and you're willing to pay a premium for versatility rather than pure aperture.
The custom-rig optical tube
William Optics · William Optics Zenithstar 73
This scope is right for you if you're primarily an astrophotographer who values capturing enormous targets — entire nebula complexes and galaxy groups — in single frames, and you're comfortable accepting that visual observing will be a secondary activity limited to the brightest objects. You'll appreciate the fast f/5.9 focal ratio's forgiving exposure times and light-polluted-sky performance, and you've already budgeted for a quality equatorial mount and the mandatory Flat73A field flattener as essential system components.
Our verdict
These two are closer than most comparisons on this site. The spec differences are genuine — mount type, focal ratio — but neither is the wrong answer for a typical observer starting out.
If I had to choose between them: the Vixen ED80Sf is the scope most people will be using regularly six months from now. The William Optics Zenithstar 73 rewards you more once you know what you're doing — it's worth revisiting after your first year.
Vixen ED80Sf
View Vixen ED80Sf →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 | Vixen ED80Sf | 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 doublet on all air-to-glass surfaces | Fully multi-coated FMC ED doublet on all air-to-glass surfaces |
How do you point it?
| Spec | Vixen ED80Sf | William Optics Zenithstar 73 |
|---|---|---|
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 | Vixen ED80Sf | 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 | Dual-speed Crayford (with 1.25" adapter) | Dual-speed Crayford 2" (10:1 reduction fine focus) |
Size & weight
| Spec | Vixen ED80Sf | William Optics Zenithstar 73 |
|---|---|---|
OTA Weightⓘ Optical tube only — useful for comparing mount load capacity | 1.8kg | 1.75kg |
Tube Length | 528mm | 320mm |
Tube Material | Aluminium | Aluminium, anodised blue |
What's in the box?
| Spec | Vixen ED80Sf | William Optics Zenithstar 73 |
|---|---|---|
Diagonal Tilts the eyepiece 90° for comfortable viewing — useful on refractors |
Blue highlight: Vixen ED80Sf advantage · Amber highlight: William Optics Zenithstar 73 advantage · Greyed cells: equal or subjective.