Telescope Comparison
Askar 80PHQ vs William Optics GT81
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 · 81mm · £699
The custom-rig optical tube
- 81mm refractor — optical tube only, no mount included
- 478mm 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 GT81 gathers 1× 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
William Optics GT81's longer focal length reaches higher magnification with the same eyepiece — better reach for planetary detail. Askar 80PHQ'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 GT81's f/5.9 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 | Askar 80PHQ | William Optics GT81 |
|---|---|---|
| Planets | ||
| Moon | Excellent 80mm aperture delivers sharp lunar detail; short focal length limits magnification but crater fields and terminator are crisp | Excellent 81mm aperture delivers sharp, high-contrast lunar detail; the triplet design keeps the terminator free of colour fringing, though the short focal length limits magnification without a Barlow |
| Saturn | Good Rings clearly visible at modest magnification; 448mm focal length limits high-power planetary detail | Moderate Rings clearly visible and colour-free, but 81mm aperture and 478mm focal length make the Cassini Division very difficult |
| Jupiter | Good Main cloud belts and Galilean moons visible, but the short focal length constrains useful magnification | Moderate Main equatorial belts visible in steady seeing; 81mm resolves limited banding detail and the Great Red Spot is marginal |
| Mars | Challenging Small disc visible at opposition; 80mm aperture and 448mm focal length insufficient to resolve surface features reliably | Challenging Small orange disc visible at opposition; 81mm aperture insufficient to resolve surface features reliably |
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 | Excellent Bright nebula easily visible; 478mm focal length at f/5.9 frames the full extent with surrounding nebulosity |
| 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 478mm focal length captures the core and dust lanes in a single wide field; aperture shows the inner halo structure |
| Open clusters | Excellent Wide field at 448mm frames large clusters like the Double Cluster, Pleiades, and Hyades superbly | Excellent Wide-field sweet spot — Pleiades, Double Cluster, and M35 are beautifully framed with colour-free stars |
| Globular clusters | Moderate 80mm aperture shows bright globulars like M13 as granular but unresolved fuzzy patches | Challenging 81mm aperture shows globulars like M13 as fuzzy balls with no individual star resolution |
| Faint galaxies | Moderate 80mm aperture detects brighter Messier galaxies as smudges; insufficient light grasp for dim NGC targets visually | Moderate Core of brighter galaxies like M81/M82 visible under dark skies, but 81mm gathers limited light for faint targets |
| Milky Way / wide field | Excellent 448mm focal length at f/5.6 — ideal for sweeping rich star fields and Milky Way structure | Excellent 478mm at f/5.9 is ideal for sweeping rich star fields; low-power eyepieces deliver expansive true fields |
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 | Good Clean optics split wider doubles cleanly with no false colour, but 81mm limits resolution on close pairs below about 1.4 arcseconds |
| 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; however, when paired with a suitable equatorial mount this becomes an excellent deep-sky imaging platform at f/5.9 |
| Astrophotography (planetary) | Challenging 80mm aperture and 448mm focal length undersized for planetary imaging; a Barlow helps but cannot overcome the aperture limit | Challenging 81mm aperture and 478mm focal length produce a small planetary image scale; limited even with a Barlow |
| 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 |
| Large emission nebulae (imaging) | Not applicable | Excellent Fast f/5.9 triplet with flat, colour-free field excels on targets like the Veil, North America Nebula, and Heart Nebula when paired with a narrowband or one-shot colour camera on a tracking mount |
The real tradeoff
Both scopes are capable. The question is which one fits the way you actually observe.
Askar 80PHQ
- You'll unpack the 80PHQ, bolt it to your equatorial mount, set your back-focus spacers to 55mm, and start shooting — no separate field flattener to buy, space, or collimate, because the integrated quadruplet design delivers flat, round stars to the corners of a full-frame sensor out of the box.
- You'll notice shorter sub-exposures stacking up faster at f/5.6 than at f/5.9, and on narrowband Ha or OIII that third-of-a-stop advantage quietly compounds across a whole night — but you're paying £100 more for a scope that's essentially purpose-built for cameras and offers very little back if you ever want to just look through an eyepiece.
- Your imaging sessions reward precision: get the spacing right and the stars are textbook pinpoints edge to edge, get it wrong by even a millimetre and you'll see field curvature creeping in at the corners — there's no forgiveness built into this optical chain.
William Optics GT81
- You'll appreciate that the GT81 pulls double duty — on a clear weeknight you can drop in a 2-inch eyepiece and sweep the Milky Way with genuinely colour-free, wide-field views, then swap to your camera on the weekend without feeling like you bought the wrong scope.
- You'll save £100 upfront, but you'll need to budget for a dedicated field flattener before your astrophotography corners look competitive with the 80PHQ's integrated optic — that's an extra £100–200 and another spacing puzzle to solve.
- You'll find the slightly longer 478mm focal length gives a touch more image scale on smaller targets like galaxy groups, but at f/5.9 your sub-exposures need a fraction more time to reach the same signal-to-noise the faster Askar achieves.
The dark side
Every scope has a personality. Here’s where each one gets difficult.
Askar
Askar 80PHQ
At £799 for the OTA alone — with no mount, finder, diagonal, or eyepiece — your total imaging system cost will easily double or triple before you capture a single photon.
Back-focus spacing must be held to approximately 55mm; even small deviations introduce field curvature and elongated corner stars, so you'll be shimming spacers and test-shooting before every new camera or filter-wheel configuration.
Some users report the stock focuser can struggle under heavy camera payloads, and an aftermarket upgrade may be needed if you're running a full-frame camera with a filter wheel and off-axis guider.
William Optics
William Optics GT81
No integrated field flattener means you must purchase and correctly space a separate corrector for astrophotography — without it, edge-of-field stars will stretch into comets on any APS-C or larger sensor.
Some production runs lack a focuser lock, so when you hang a heavy imaging train on the drawtube, gravity can slowly pull focus during long exposures — verify your unit has one or add a focuser lock accessory.
At 81mm aperture and 478mm focal length, high-magnification visual use requires very short focal-length eyepieces or a Barlow that can compromise eye relief, and even then planetary detail is sparse — the Cassini Division on Saturn remains elusive.
Which is right for you?
Two different buyers. Two different right answers.
The custom-rig optical tube
Askar · Askar 80PHQ
You'll love the 80PHQ if you already own an equatorial mount and autoguider and you want a compact, dedicated imaging refractor that delivers flat, corrected fields on a full-frame sensor with zero accessory headaches. You're optimising for astrophotography and only astrophotography — you don't expect to use this scope visually in any meaningful way, and you're willing to pay the premium for an integrated quadruplet design that eliminates the flattener-spacing game. This isn't for you if you want any visual capability, if you're on a tight budget that doesn't include a mount and accessories, or if you need longer focal length for small galaxy or planetary imaging.
The custom-rig optical tube
William Optics · William Optics GT81
You'll love the GT81 if you want a versatile, colour-free APO that rewards both casual visual sweeping and serious wide-field astrophotography, and you don't mind sourcing a separate field flattener to get the best imaging performance. You're the kind of observer who'll point it at the Double Cluster on a Tuesday night and shoot the Veil Nebula on Saturday, and the £100 savings over the Askar helps fund that flattener. This isn't for you if you want a pure, optimised imaging pipeline out of the box — you'll be buying and spacing a flattener yourself — or if you need aperture for planetary or faint-galaxy visual work.
Our verdict
Same aperture, same light-gathering, £100 price difference. The extra cost of the Askar 80PHQ buys a different mount — not better optics.
For most beginners, the William Optics GT81 is the right starting point — the optics are identical and the savings are better spent on a quality eyepiece or a dark-sky trip. The Askar 80PHQ makes sense if the mount it comes with is specifically what you want to learn. If I had to choose: the William Optics GT81 — same sky, less money.
Askar 80PHQ
View Askar 80PHQ →William Optics GT81
View William Optics GT81 →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 GT81 |
|---|---|---|
Apertureⓘ The most important spec — bigger = more light = better views | 80mm | 81mm |
Focal Length Longer = more magnification potential | 448mm | 478mm |
Focal Ratio Lower f-number = wider field of view; higher = more magnification per eyepiece | f/5.6 | 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 PHQ quadruplet on all surfaces | Fully multi-coated FMC ED triplet on all air-to-glass surfaces |
How do you point it?
| Spec | Askar 80PHQ | William Optics GT81 |
|---|---|---|
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 GT81 |
|---|---|---|
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 GT81 |
|---|---|---|
OTA Weightⓘ Optical tube only — useful for comparing mount load capacity | 2.8kg | 2.5kg |
Tube Length | 360mm | 380mm |
Tube Material | Aluminium | Aluminium, anodised |
What's in the box?
| Spec | Askar 80PHQ | William Optics GT81 |
|---|---|---|
Diagonal Tilts the eyepiece 90° for comfortable viewing — useful on refractors |
Blue highlight: Askar 80PHQ advantage · Amber highlight: William Optics GT81 advantage · Greyed cells: equal or subjective.