Telescope Comparison
Askar 103APO vs Sky-Watcher Esprit 100ED
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
Sky-Watcher · 100mm · £1,099
The custom-rig optical tube
- 100mm refractor — optical tube only, no mount included
- 550mm focal length at f/5.5
- 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
Askar 103APO gathers 1.1× 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
Askar 103APO's longer focal length reaches higher magnification with the same eyepiece — better reach for planetary detail. Sky-Watcher Esprit 100ED's shorter focal length gives a wider true field — better for large open clusters and extended nebulae.
Focal ratio
Sky-Watcher Esprit 100ED's faster f/5.5 delivers wider fields with any eyepiece — better for open clusters and large nebulae. Askar 103APO's f/6.8 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 | Sky-Watcher Esprit 100ED |
|---|---|---|
| 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 100mm aperture delivers sharp crater detail and clean terminator views; the fast focal ratio means lower magnification per eyepiece but detail is still crisp |
| 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 clearly separated, Cassini Division visible in good seeing; 550mm focal length limits image scale at the eyepiece |
| 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; 100mm aperture resolves belt detail but the short focal length caps useful magnification |
| 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 and polar cap visible at opposition; 100mm and 550mm focal length are limiting for surface albedo features |
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 100mm gathers ample light, 550mm frames the full nebula with surrounding nebulosity; f/5.5 rewards both visual and imaging use |
| 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 550mm captures the full extent of M31 including companion galaxies; 100mm aperture shows outer halo hints visually |
| Open clusters | Excellent 700mm focal length and wide true field frame showpiece clusters like the Double Cluster and Pleiades beautifully | Excellent 550mm focal length provides generous framing — the Double Cluster, Pleiades, and similar targets are beautifully presented |
| 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 and M5 appear granular with hints of edge resolution; core remains unresolved at 100mm |
| Faint galaxies | Moderate 103mm aperture detects brighter Messier galaxies as smudges but struggles with fainter NGC targets visually | Moderate 100mm shows brighter Messier galaxies as fuzzy patches; NGC targets require dark skies and are at the limit 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 550mm is slightly long for sweeping Milky Way panoramas but still delivers rich star fields; excellent for targeted regions like Cygnus |
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 | Good 100mm resolves down to about 1.2 arcsec; chromatic correction is excellent but the fast focal ratio makes splitting tight pairs trickier than in a long-focus refractor |
| 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 included — on a suitable equatorial GoTo mount this scope would rate Excellent (f/5.5, 100mm, flat field to full-frame), but as sold it cannot track |
| 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 100mm aperture is workable with a Barlow and planetary camera, but 550mm native focal length requires significant amplification; needs a tracking mount |
| 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 | Excellent Fast f/5.5 ratio and 550mm focal length are ideal for large emission targets like the Veil, Rosette, and Heart Nebulae on APS-C or full-frame sensors |
| 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 | Good 550mm frames targets like the Leo Triplet and Markarian's Chain well on APS-C; 100mm gathers enough light for reasonable exposure times |
The real tradeoff
Both scopes are capable. The question is which one fits the way you actually observe.
Askar 103APO
- You'll get a longer 700mm focal length that pulls more detail out of medium-sized galaxies like M81/M82 and the Leo Triplet — but you'll pay for it with longer exposure times at f/6.8, so you're spending more time per sub and more total integration time to match the signal the Esprit gathers at f/5.5.
- You'll need to buy a separate field flattener or reducer and nail the correct spacing yourself — an extra purchase and an extra calibration step every time you reassemble the imaging train, whereas the Esprit's integrated flattener simplifies your setup ritual considerably.
- You're investing in a slightly larger 103mm aperture that gathers marginally more light, but the real-world difference over the Esprit's 100mm is negligible — your choice here is really about focal length and framing preference, not light-gathering advantage.
Sky-Watcher Esprit 100ED
- You'll frame dramatically wider fields at 550mm — the entire Veil Nebula complex, the full extent of Andromeda — and at f/5.5 you're gathering usable signal roughly 50% faster per sub than the Askar at f/6.8, which means shorter exposures or better signal-to-noise on any given night.
- You'll appreciate the integrated field flattener that's factory-optimised for 55mm back-focus — set your spacing once and you get flat stars to the corners without sourcing a third-party flattener, though you absolutely must get that 55mm distance right or your edges will suffer.
- You'll save £100 on the OTA and likely end up with a lighter imaging train, making it easier to stay within your mount's payload rating — which matters when you're loading on a guidescope, camera, and filter wheel at 2am in the cold.
The dark side
Every scope has a personality. Here’s where each one gets difficult.
Askar
Askar 103APO
At f/6.8, the Askar is notably slower than the Esprit's f/5.5 — you'll need roughly 50% longer exposures to reach equivalent signal, which compounds across a full night of imaging and demands better tracking from your mount.
You must buy a matched field flattener or reducer separately to get sharp edge stars on APS-C or full-frame sensors — an additional cost and a potential source of spacing errors that the Esprit avoids with its integrated flattener.
The OTA alone is £1199 with no mount, no diagonal, no eyepieces — budget realistically for £3000+ once you add a capable equatorial mount, guide system, and camera, making this one of the more expensive entry points into dedicated imaging.
Sky-Watcher
Sky-Watcher Esprit 100ED
At 550mm focal length, planetary image scale is small — if you ever want to shoot Jupiter or Saturn, you'll find the Esprit severely limited compared to longer focal length instruments, and the Askar's extra 150mm doesn't help much either.
The integrated field flattener is optimised for exactly 55mm back-focus — get the spacing wrong by even a couple of millimetres and you'll see elongated stars at the field edges, so you'll spend real time with spacer rings and a ruler before your first exposure.
Some narrowband filters produce halos or uneven illumination at f/5.5 across full-frame sensors — if you're planning to shoot in Ha or OIII on a full-frame camera, test your filter set carefully or plan to crop to APS-C.
Which is right for you?
Two different buyers. Two different right answers.
The custom-rig optical tube
Askar · Askar 103APO
You want the Askar 103APO if you're an intermediate astrophotographer who's outgrown an 80mm refractor and you specifically want more focal length to frame galaxy groups and smaller nebulae with better resolution. You're comfortable sourcing and spacing a separate field flattener, you already own a mount rated for 6kg+ imaging payloads, and you don't mind the slower f/6.8 speed because you're patient with integration time. You're not looking for a visual scope and you're not on a tight budget — you understand this OTA is the centrepiece of a £3000+ system.
The custom-rig optical tube
Sky-Watcher · Sky-Watcher Esprit 100ED
You want the Esprit 100ED if you're chasing wide-field nebula targets and want to gather data fast at f/5.5 without fussing over a separate field flattener. You value the simplicity of an integrated optical design where you set 55mm back-focus and go, and you appreciate the lighter weight keeping you safely within your mount's imaging payload. You're shooting primarily on APS-C or are willing to test narrowband filters carefully on full-frame. This isn't for you if you want tighter framing on galaxies or need a grab-and-go visual setup — it's a dedicated imaging platform that costs £100 less than the Askar but demands the same expensive supporting ecosystem.
Our verdict
Same aperture, same light-gathering, £100 price difference. The extra cost of the Askar 103APO buys a different mount — not better optics.
For most beginners, the Sky-Watcher Esprit 100ED 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 Sky-Watcher Esprit 100ED — same sky, less money.
Askar 103APO
View Askar 103APO →Sky-Watcher Esprit 100ED
View Sky-Watcher Esprit 100ED →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 | Sky-Watcher Esprit 100ED |
|---|---|---|
Apertureⓘ The most important spec — bigger = more light = better views | 103mm | 100mm |
Focal Length Longer = more magnification potential | 700mm | 550mm |
Focal Ratio Lower f-number = wider field of view; higher = more magnification per eyepiece | f/6.8 | f/5.5 |
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 triplet on all air-to-glass surfaces | Fully multi-coated ED triplet with FMC on all air-to-glass surfaces |
How do you point it?
| Spec | Askar 103APO | Sky-Watcher Esprit 100ED |
|---|---|---|
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 | Sky-Watcher Esprit 100ED |
|---|---|---|
Focuser Size 2" accepts wider eyepieces and gives better low-power views | 2" / 1.25" | 2" |
Focuser Type Rack-and-pinion is standard; Crayford and dual-speed are smoother | Dual-speed Crayford 2" (10:1 reduction) | Dual-speed Crayford (10:1 reduction, with 1.25" adapter) |
Size & weight
| Spec | Askar 103APO | Sky-Watcher Esprit 100ED |
|---|---|---|
OTA Weightⓘ Optical tube only — useful for comparing mount load capacity | 3.8kg | 3.9kg |
Tube Length | 550mm | 535mm |
Tube Material | Aluminium | Aluminium, white powder coat |
What's in the box?
| Spec | Askar 103APO | Sky-Watcher Esprit 100ED |
|---|---|---|
Diagonal Tilts the eyepiece 90° for comfortable viewing — useful on refractors |
Blue highlight: Askar 103APO advantage · Amber highlight: Sky-Watcher Esprit 100ED advantage · Greyed cells: equal or subjective.