Telescope Comparison
Askar 103APO vs William Optics GT102
The specs are close. The experience isn't.
First light
Askar · 103mm · £1,199
The custom-rig optical tube
- 103mm refractor — optical tube only, no mount included
- 700mm focal length at f/6.8
- 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 · 102mm · £999
The custom-rig optical tube
- 102mm refractor — optical tube only, no mount included
- 714mm focal length at f/7
- 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 103APO 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 GT102's longer focal length reaches higher magnification with the same eyepiece — better reach for planetary detail. Askar 103APO's shorter focal length gives a wider true field — better for large open clusters and extended nebulae.
Focal ratio
Askar 103APO's faster f/6.8 delivers wider fields with any eyepiece — better for open clusters and large nebulae. William Optics GT102's f/7 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 103APO | William Optics GT102 |
|---|---|---|
| Planets | ||
| Moon | Excellent 103mm aperture delivers sharp crater detail and clean terminator views; the ED triplet produces essentially no chromatic fringing on the bright limb | Excellent 102mm APO delivers razor-sharp, colour-free lunar detail; f/7 rewards medium-high magnifications cleanly |
| Saturn | Good Rings clearly defined, Cassini Division visible in steady seeing; 700mm focal length supports useful magnification but aperture limits fine banding detail | Good Rings well-defined, Cassini Division visible in steady seeing; 714mm focal length limits image scale for fine detail |
| Jupiter | Good Two main equatorial belts and GRS visible; 103mm resolves some secondary belts in good seeing but can't match larger apertures for fine atmospheric detail | Good Two main cloud belts and GRS visible with no chromatic aberration; a Barlow extends reach for more detail |
| Mars | Moderate Small disc visible with polar cap detectable near opposition; 103mm and 700mm focal length limit the detail available on this demanding target | Moderate Disc visible with polar cap at opposition; 102mm aperture limits surface albedo detail |
Deep sky | ||
| Orion Nebula (M42) | Excellent 103mm gathers plenty of light and 700mm focal length frames the full nebula complex well; Trapezium resolved and nebulosity extends visually | Excellent 102mm gathers ample light; 714mm frames the full nebula extent with surrounding context |
| Andromeda Galaxy (M31) | Excellent 700mm focal length keeps the full extent of M31 in the field; 103mm aperture shows the bright core and hints of dust lanes | Excellent 714mm focal length captures the bright core and extended halo; 102mm aperture aids outer arm visibility |
| Open clusters | Excellent 700mm focal length and wide true field frame showpiece clusters like the Double Cluster and Pleiades beautifully | Excellent Wide field at 714mm frames clusters like the Double Cluster beautifully with pinpoint stars |
| Globular clusters | Moderate 103mm shows a granular, textured ball but cannot resolve individual stars in the core; M13 and M3 appear mottled at best | Moderate M13 appears granular with a bright unresolved core; 102mm cannot resolve individual stars throughout |
| Faint galaxies | Moderate 103mm aperture detects brighter Messier galaxies as smudges but struggles with fainter NGC targets visually | Moderate 102mm aperture shows brighter Messier galaxies as fuzzy patches; fainter NGC targets need more aperture visually |
| Milky Way / wide field | Good 700mm is slightly long for sweeping starfield views but still delivers rich fields; a reducer brings it closer to wide-field territory | Good 714mm is at the upper end for star-field sweeping; rich fields are enjoyable but the true field is narrower than sub-500mm scopes |
Other | ||
| Double stars | Good 103mm resolves doubles to about 1.1 arcsecond; f/6.8 is not ideal for high-magnification splitting but the clean optics help | Excellent 102mm resolves to ~1.1 arcsec; clean APO optics give textbook Airy discs and tight diffraction-limited splits |
| Astrophotography (deep sky) | Not recommended No mount or tracking included; with a suitable equatorial mount this scope would rate Excellent — f/6.8, 103mm aperture, and ED triplet design are ideal for deep-sky imaging | Not recommended No mount or tracking included — requires separate equatorial mount purchase; on a suitable mount this OTA would rate Excellent at f/7 with triplet correction |
| Astrophotography (planetary) | Moderate 103mm aperture captures reasonable planetary detail with a high-speed camera, but aperture and focal length limit resolution compared to larger scopes | Moderate 102mm aperture limits planetary detail capture; focal length benefits from a 2–3× Barlow for adequate image scale |
| Emission nebulae (imaging) | Excellent 700mm at f/6.8 frames large emission nebulae like the Heart, Soul, and North America Nebula well on APS-C sensors; tight star correction across the field with a matched flattener | Not applicable |
| Galaxy groups (imaging) | Good 700mm focal length provides enough scale for galaxy groups like the Leo Triplet or M81/M82 on common sensor sizes while keeping good signal-to-noise at f/6.8 | Not applicable |
The real tradeoff
Both scopes are capable. The question is which one fits the way you actually observe.
Askar 103APO
- You're paying £200 more for a scope that's fractionally faster at f/6.8 versus f/7 — in practice, that saves you maybe a minute or two per sub-exposure on faint emission nebulae, not a dramatic difference but a real one over a night of integration.
- You'll be hauling a heavier OTA (5–6kg with accessories versus the GT102's ~4kg base weight), which means your mount margin shrinks — if you're on an HEQ5, you'll feel the difference in guiding residuals and you'll be more tempted to upgrade to an EQ6-class sooner.
- Your imaging sessions reward you with very tight stars and strong colour correction, but you're buying into Askar's accessory ecosystem for field flatteners and reducers — make sure the matched flattener is actually in stock before you commit.
William Optics GT102
- You're saving £200 upfront and getting a lighter OTA, which means your HEQ5 breathes easier and your guiding is more forgiving — you'll notice this on windy nights or when you're pushing longer focal lengths with a Barlow for planetary snapshots.
- You'll find yourself reaching for this scope visually more often than you expected — William Optics builds refractors that feel like visual instruments even when they're designed for imaging, and the colour-free star fields through an eyepiece are genuinely rewarding on grab-and-go nights.
- You may hit the focuser limitation: some production runs lack a focuser lock, so if you're imaging at longer exposures or swapping heavy cameras, you'll want to budget for a motor focuser upgrade early to avoid tilt-induced star elongation ruining your subs.
The dark side
Every scope has a personality. Here’s where each one gets difficult.
Askar
Askar 103APO
At £1199 for the OTA alone, your total imaging rig — mount, camera, flattener, guide scope, guide camera — will comfortably exceed £3000 before you capture a single photon.
The f/6.8 focal ratio is moderately fast but noticeably slower than dedicated f/5 astrographs, so on faint extended targets like the Veil Nebula you'll need substantially longer total integration to match the signal-to-noise of a faster system.
At 5–6kg fully loaded, you're right at the practical payload limit of popular mid-range mounts like the HEQ5 — guiding performance can suffer, pushing you toward a more expensive mount sooner than planned.
William Optics
William Optics GT102
Some production runs ship without a focuser lock, meaning your imaging train can shift under gravity loads when you change target altitude — an aftermarket motor focuser isn't optional, it's essential for reliable imaging.
Full-frame sensor users will see noticeable edge star distortion without the matched William Optics field flattener, which adds to your already substantial accessory bill on top of a scope sold with no mount, finder, or diagonal.
At f/7 and 714mm, you're slower than most dedicated wide-field imaging APOs — you'll feel this on large emission nebulae where faster systems accumulate signal meaningfully quicker per sub-exposure.
Which is right for you?
Two different buyers. Two different right answers.
The custom-rig optical tube
Askar · Askar 103APO
You've already been imaging with an 80mm APO, you know exactly what an HEQ5 can carry, and you want the tightest possible colour correction at a focal length that frames galaxies and medium nebulae well on APS-C. You don't flinch at the total system cost because you already own most of the supporting gear and you're buying the Askar specifically for its imaging optics, not for visual use. If you value that fractional speed advantage at f/6.8 and you're prepared to manage the extra weight, this is your next OTA.
The custom-rig optical tube
William Optics · William Optics GT102
You want a triplet APO that pulls double duty — primarily an imaging refractor, but also a scope you'll genuinely enjoy looking through on nights when you don't feel like setting up the full imaging chain. You appreciate that £200 saved on the OTA can go toward a flattener or motor focuser, and the lighter weight gives you real headroom on your existing mount. If you're stepping up from a smaller refractor and want clean optics without overloading your budget or your payload capacity, the GT102 is the pragmatic choice — just plan on that focuser upgrade early.
Our verdict
Same aperture, same light-gathering, £200 price difference. The extra cost of the Askar 103APO buys a different mount — not better optics.
For most beginners, the William Optics GT102 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 103APO makes sense if the mount it comes with is specifically what you want to learn. If I had to choose: the William Optics GT102 — same sky, less money.
Askar 103APO
View Askar 103APO →William Optics GT102
View William Optics GT102 →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 103APO | William Optics GT102 |
|---|---|---|
Apertureⓘ The most important spec — bigger = more light = better views | 103mm | 102mm |
Focal Length Longer = more magnification potential | 700mm | 714mm |
Focal Ratio Lower f-number = wider field of view; higher = more magnification per eyepiece | f/6.8 | f/7 |
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 triplet on all air-to-glass surfaces | Fully multi-coated FMC ED triplet on all air-to-glass surfaces |
How do you point it?
| Spec | Askar 103APO | William Optics GT102 |
|---|---|---|
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 103APO | William Optics GT102 |
|---|---|---|
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" (10:1 reduction) | Dual-speed Crayford 2" (10:1 reduction fine focus) |
Size & weight
| Spec | Askar 103APO | William Optics GT102 |
|---|---|---|
OTA Weightⓘ Optical tube only — useful for comparing mount load capacity | 3.8kg | 4kg |
Tube Length | 550mm | 565mm |
Tube Material | Aluminium | Aluminium, anodised |
What's in the box?
| Spec | Askar 103APO | William Optics GT102 |
|---|---|---|
Diagonal Tilts the eyepiece 90° for comfortable viewing — useful on refractors |
Blue highlight: Askar 103APO advantage · Amber highlight: William Optics GT102 advantage · Greyed cells: equal or subjective.