Telescope Comparison
Askar 80PHQ vs William Optics Zenithstar 73
The specs are close. The experience isn't.
First light
Askar · 80mm · £799
The custom-rig optical tube
- 80mm refractor — optical tube only, no mount included
- 448mm focal length at f/5.6
- 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
Askar 80PHQ 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
Askar 80PHQ'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
Askar 80PHQ's faster f/5.6 delivers wider fields with any eyepiece — better for open clusters and large nebulae. William Optics Zenithstar 73's f/5.89 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)
William Optics Zenithstar 73'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 | Askar 80PHQ | William Optics Zenithstar 73 |
|---|---|---|
| Planets | ||
| Moon | Excellent 80mm aperture delivers sharp lunar detail; short focal length limits magnification but crater fields and terminator are crisp | 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 visible at modest magnification; 448mm focal length limits high-power planetary detail | 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 cloud belts and Galilean moons visible, but the short focal length constrains useful magnification | 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 disc visible at opposition; 80mm aperture and 448mm focal length insufficient to resolve surface features reliably | 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 Bright target framed beautifully by the wide field; f/5.6 speed and sub-600mm focal length show full nebula extent | 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 448mm focal length captures the full extent of M31 including outer halo; 80mm aperture adequate for the bright core and dust lanes | 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 at 448mm frames large clusters like the Double Cluster, Pleiades, and Hyades superbly | 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 80mm aperture shows bright globulars like M13 as granular but unresolved fuzzy patches | Challenging 73mm aperture shows M13 and M22 as fuzzy unresolved glows — no star resolution possible at this aperture. |
| Faint galaxies | Moderate 80mm aperture detects brighter Messier galaxies as smudges; insufficient light grasp for dim NGC targets visually | Challenging 73mm gathers limited light; only the brightest galaxies like M81/M82 show as faint smudges visually. |
| Milky Way / wide field | Excellent 448mm focal length at f/5.6 — ideal for sweeping rich star fields and Milky Way structure | 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 80mm resolves wider doubles cleanly; the fast f/5.6 focal ratio is less ideal than a long-FL refractor for tight pairs | 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 recommended OTA only with no mount — requires a separate equatorial or GoTo mount for any deep-sky imaging; on a suitable mount this would rate Excellent | 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 448mm focal length undersized for planetary imaging; a Barlow helps but cannot overcome the aperture limit | Challenging 73mm aperture and 430mm focal length produce a very small planetary image scale — a Barlow helps but aperture is the fundamental limit. |
| Wide-field emission nebulae (imaging) | Excellent Fast f/5.6 quad APO with integrated flattener is purpose-built for targets like the Veil, North America, and Rosette Nebulae on a suitable mount | Not applicable |
The real tradeoff
Both scopes are capable. The question is which one fits the way you actually observe.
Askar 80PHQ
- You'll unbox this, attach your camera, nail the 55mm back-focus spacing, and start shooting — the integrated quadruplet field flattener means no hunting for a separate corrector, no extra spacer math, and no wondering why your corner stars look like seagulls.
- You're paying a £200 premium over the Zenithstar 73 to skip the 'which flattener do I need?' phase entirely — and you get genuinely flat, round stars across a full-frame sensor straight out of the box, which the ZS73 simply cannot match without its dedicated Flat73A.
- You'll notice the extra 7mm of aperture and slightly faster f/5.6 speed are marginal gains on paper, but the real reward is in the optical design: a quadruplet APO versus an ED doublet means cleaner colour correction on bright stars and less post-processing time fighting purple halos.
William Optics Zenithstar 73
- You'll spend less upfront on the OTA, but you need to budget another £200+ for the Flat73A field flattener before your images look right — skip it and your field edges will punish you with coma and curvature that no amount of post-processing will fix cleanly.
- You'll find this scope is almost absurdly portable — at 73mm it's one of the lightest serious imaging refractors you can own, meaning you can pair it with a lighter, cheaper equatorial mount and still get sharp results on shorter exposures.
- You'll get surprisingly pleasant quick-look visual sessions on the Moon, bright clusters, and M42, but you'll hit the aperture wall fast — don't expect to resolve anything faint, and accept that the ED doublet design may show faint colour fringing on the brightest stars that the 80PHQ's quadruplet design suppresses.
The dark side
Every scope has a personality. Here’s where each one gets difficult.
Askar
Askar 80PHQ
The 55mm back-focus spacing is critical and unforgiving — get it wrong by even a millimetre or two and the flat-field advantage you paid for evaporates into field curvature and elongated corner stars.
Some users report the stock focuser can struggle with heavier camera and filter-wheel payloads, potentially requiring an aftermarket upgrade that adds to an already mount-less, accessory-less purchase price.
At 80mm, you're still working with modest light grasp — faint targets demand long total integration times compared to 100–130mm class APO refractors, so plan for longer sessions or more nights of stacking.
William Optics
William Optics Zenithstar 73
The dedicated Flat73A field flattener is essentially mandatory for imaging — without it, edge-of-field star quality degrades noticeably, making it a hidden cost that closes the price gap with the 80PHQ.
As an ED doublet rather than a triplet or quadruplet, residual chromatic aberration on bright stars is a known trade-off — you may see violet or magenta halos in images that a higher-order design like the 80PHQ largely eliminates.
The 2-inch rack-and-pinion focuser can exhibit minor flexure under heavier imaging payloads, requiring careful balancing and potentially limiting the filter trains you can hang off the back without introducing shift.
Which is right for you?
Two different buyers. Two different right answers.
The custom-rig optical tube
Askar · Askar 80PHQ
You want a compact deep-sky imaging refractor that arrives ready to bolt onto your camera with no separate flattener to buy, no corrector spacing to second-guess, and no compromises on full-frame corner sharpness. You've already got a mount, a guide scope, and a processing workflow — you're not looking for a beginner package, you're looking for an optical tube that earns its keep on the first clear night. You're willing to pay the £200 premium over the ZS73 because you value the quadruplet APO's cleaner colour correction and integrated flat-field design over saving money now and buying a flattener later.
The custom-rig optical tube
William Optics · William Optics Zenithstar 73
You're building your first dedicated astrophotography rig on a budget and you want the lowest-cost entry point into serious wide-field imaging with a quality refractor. You don't mind buying the Flat73A flattener separately because you understand the total system cost is still competitive, and you value the ZS73's extreme portability — it pairs with lighter, less expensive mounts, making your whole kit easier to transport to dark-sky sites. You can live with an ED doublet's minor chromatic aberration trade-offs because you know narrowband and careful processing will handle most of it, and you'd rather put the savings toward mount quality or a better camera.
Our verdict
At similar price points, these scopes offer different amounts of aperture per pound. The William Optics Zenithstar 73 gives you more light-gathering for your money — and for visual observing, aperture per pound is the most useful single metric.
For pure optical value, the William Optics Zenithstar 73 is the stronger pick. The Askar 80PHQ compensates with other features — decide whether those trade-offs justify the premium. If I had to choose: the William Optics Zenithstar 73 — more aperture per pound means more sky.
Askar 80PHQ
View Askar 80PHQ →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 | Askar 80PHQ | William Optics Zenithstar 73 |
|---|---|---|
Apertureⓘ The most important spec — bigger = more light = better views | 80mm | 73mm |
Focal Length Longer = more magnification potential | 448mm | 430mm |
Focal Ratio Lower f-number = wider field of view; higher = more magnification per eyepiece | f/5.6 | 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 PHQ quadruplet on all surfaces | Fully multi-coated FMC ED doublet on all air-to-glass surfaces |
How do you point it?
| Spec | Askar 80PHQ | 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 | Askar 80PHQ | William Optics Zenithstar 73 |
|---|---|---|
Focuser Size 2" accepts wider eyepieces and gives better low-power views | 2" / 1.25" | 2" / 1.25" |
Focuser Type Rack-and-pinion is standard; Crayford and dual-speed are smoother | Dual-speed Crayford 2" (with 1.25" adapter) | Dual-speed Crayford 2" (10:1 reduction fine focus) |
Size & weight
| Spec | Askar 80PHQ | William Optics Zenithstar 73 |
|---|---|---|
OTA Weightⓘ Optical tube only — useful for comparing mount load capacity | 2.8kg | 1.75kg |
Tube Length | 360mm | 320mm |
Tube Material | Aluminium | Aluminium, anodised blue |
What's in the box?
| Spec | Askar 80PHQ | William Optics Zenithstar 73 |
|---|---|---|
Diagonal Tilts the eyepiece 90° for comfortable viewing — useful on refractors |
Blue highlight: Askar 80PHQ advantage · Amber highlight: William Optics Zenithstar 73 advantage · Greyed cells: equal or subjective.