Telescope Comparison
Askar 151PHQ vs Sky-Watcher Esprit 120ED
The specs are close. The experience isn't.
First light
Askar · 151mm · £1,999
The custom-rig optical tube
- 151mm refractor — optical tube only, no mount included
- 1057mm 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
Sky-Watcher · 120mm · £1,699
The custom-rig optical tube
- 120mm refractor — optical tube only, no mount included
- 840mm 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 151PHQ gathers 1.6× 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 151PHQ's longer focal length reaches higher magnification with the same eyepiece — better reach for planetary detail. Sky-Watcher Esprit 120ED's shorter focal length gives a wider true field — better for large open clusters and extended nebulae.
Focal ratio
Same focal ratio — the same eyepiece gives equivalent magnification and true field in both scopes.
Mount type
Neither scope includes a mount — both require a separate purchase before you can observe.
Weight (OTA)
Sky-Watcher Esprit 120ED's optical tube is 3.8kg 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 151PHQ | Sky-Watcher Esprit 120ED |
|---|---|---|
| Planets | ||
| Moon | Excellent 151mm aperture and 1057mm focal length deliver very high-contrast lunar detail — though this scope is rarely used for visual work | Excellent 120mm apochromatic optics deliver razor-sharp lunar detail with zero chromatic aberration — craterlets and rilles cleanly resolved |
| Saturn | Excellent 151mm aperture and 1057mm focal length exceed the thresholds — Cassini Division and cloud banding visible in steady seeing | Good 120mm aperture and 840mm focal length show rings, Cassini Division in steady seeing, and subtle banding on the disc |
| Jupiter | Excellent Cloud belts, the Great Red Spot, and moon transits well resolved at this aperture and focal length | Good Cloud bands, Great Red Spot, and moon transits visible — the clean apo optics give high contrast, though aperture limits finest detail |
| Mars | Good 151mm aperture shows polar caps and major surface albedo features at opposition, but falls short of the 200mm threshold for excellent | Moderate Disc visible with polar cap and dark albedo features at opposition, but 120mm limits fine surface detail |
Deep sky | ||
| Orion Nebula (M42) | Good 151mm aperture renders bright nebulosity easily, but the 1057mm focal length limits the wide-field context that shows the full extent of the nebula | Excellent 120mm aperture reveals nebulosity easily; 840mm focal length frames the core and wings well on camera or in a wide-field eyepiece |
| Andromeda Galaxy (M31) | Moderate At 1057mm focal length the outer halo is significantly cropped — only the bright core and inner disc fit in the field | Good 840mm focal length captures the bright core and inner spiral arms but crops the full 3° extent on most sensors and eyepieces |
| Open clusters | Moderate 1057mm focal length means large open clusters like the Double Cluster or Pleiades overfill the field of view | Good 840mm gives a pleasing field for medium-sized clusters like M35 and the Double Cluster, though the largest clusters may not fully fit |
| Globular clusters | Good 151mm aperture gives partial resolution of outer stars in brighter globulars like M13 and M22 | Moderate 120mm resolves granularity at the edges of brighter globulars like M13, but the core remains unresolved |
| Faint galaxies | Good 151mm of refractor aperture with excellent contrast — galaxy cores and spiral hints visible visually, and the scope truly excels here in imaging mode | Moderate 120mm gathers enough light to detect many Messier and brighter NGC galaxies, but faint detail requires long imaging exposures |
| Milky Way / wide field | Not recommended 1057mm focal length is far too narrow for sweeping Milky Way star fields | Moderate 840mm focal length is too narrow for sweeping Milky Way vistas — better suited to individual targets within it |
Other | ||
| Double stars | Excellent 151mm aperture resolves to approximately 0.8 arcseconds; clean refractor optics give tight, high-contrast Airy patterns | Excellent 120mm aperture resolves to ~1 arcsecond; the apochromatic design produces clean, colour-free Airy discs ideal for tight doubles |
| Astrophotography (planetary) | Good 151mm aperture and 1057mm focal length — effective with a 2–3× Barlow, though a tracking mount is needed and aperture falls short of 200mm for excellent | Moderate 120mm aperture limits planetary resolution compared to larger scopes; 840mm native focal length benefits from a 2–3× Barlow for better image scale |
| Galaxy imaging (deep sky) | Excellent The ideal use case — 1057mm at f/7 with an integrated flat field gives sharp, well-corrected galaxy images across a full-frame sensor when paired with a capable equatorial mount | Not applicable |
| Planetary nebula imaging | Excellent The longer focal length provides meaningful image scale on small targets like M27, M57, and NGC 7662, with enough aperture to capture faint outer halos | Not applicable |
| Compact emission and planetary nebulae | Not applicable | Excellent 840mm focal length and f/7 speed are ideal for imaging targets like the Crescent Nebula, Veil Nebula panels, and the Dumbbell Nebula |
The real tradeoff
Both scopes are capable. The question is which one fits the way you actually observe.
Askar 151PHQ
- You'll spend your setup time wrestling with balance — at 10–11kg before you bolt on a camera and guide scope, the 151PHQ demands a serious mount like an EQ6-R or better, and you'll feel every gram when you're shimming counterweights at 2am.
- You're rewarded with 151mm of aperture in a refractor, which means your galaxy season subs will show spiral arm detail and HII region texture that the Esprit 120 simply can't match at the same integration time — the extra 31mm of aperture collects roughly 58% more light.
- You'll feel the 1057mm focal length in your guiding graph: every gust of wind and every periodic error spike is magnified, so you'll need an off-axis guider or a rigidly mounted guide scope and the patience to dial in your guiding to sub-arcsecond RMS before you can trust a 5-minute exposure.
Sky-Watcher Esprit 120ED
- You'll actually be able to carry this to a dark site without dreading the trip — at roughly 5.5kg for the OTA, the Esprit 120 rides comfortably on an HEQ5 or similar mid-range mount, and your total imaging payload stays manageable enough that polar alignment and balancing don't eat half the night.
- You'll find the 840mm focal length more forgiving of your guiding setup: the shorter reach means periodic error and wind shake are less punishing, so you'll get usable subs on nights when the 151PHQ owner next to you is binning frames.
- You're trading reach for field of view — at 840mm on a full-frame sensor you can frame larger targets like the Heart and Soul or North America Nebula in a single shot, while the Askar's 1057mm would crop them significantly.
The dark side
Every scope has a personality. Here’s where each one gets difficult.
Askar
Askar 151PHQ
The OTA ships with nothing — no mount, no finder, no diagonal, no eyepieces — and at £1,999 for the tube alone, you'll need to budget at least another £2,000–£3,000 for a mount rated to handle the 20kg+ imaging payload.
At approximately 10–11kg before accessories, the 151PHQ pushes mid-range mounts like the HEQ5 well past their imaging payload limits — you're essentially locked into EQ6-class or heavier hardware, with all the cost and weight that entails.
The f/7 focal ratio is slower than many dedicated astrographs at f/4 or f/5, so you'll need significantly longer total integration times to reach the same signal-to-noise ratio, especially on faint broadband targets.
Sky-Watcher
Sky-Watcher Esprit 120ED
Like the Askar, this is an OTA-only purchase with no mount, diagonal, or eyepieces — total system cost with a capable equatorial mount and camera setup will typically exceed £4,000.
At 840mm focal length, autoguiding is non-negotiable for anything beyond very short exposures — this is not a grab-and-go imaging setup despite its relatively portable weight.
Some users report the retractable dew shield mechanism becomes stiff in cold conditions, which is exactly when you need it to extend smoothly to prevent dew from ruining a session.
Which is right for you?
Two different buyers. Two different right answers.
The custom-rig optical tube
Askar · Askar 151PHQ
You already own a serious equatorial mount rated to 25kg or more, you've mastered autoguiding, and you want the largest high-quality refractor aperture you can get for resolving fine detail in galaxies and compact nebulae. You're not fazed by a heavy OTA, you image from a fixed observatory or a site where you don't have to carry gear far, and you're willing to invest in longer integration times at f/7 because you know the five-element corrected field will deliver clean stars across a full-frame sensor without post-processing pain. This isn't for you if you're building your first imaging rig, if you value portability, or if you don't already have the mount to support it.
The custom-rig optical tube
Sky-Watcher · Sky-Watcher Esprit 120ED
You're an experienced astrophotographer who wants a premium refractor that balances imaging quality with real-world portability — you travel to dark sites, you want a scope that rides your HEQ5 or EQ6 without maxing it out, and you value a wider field of view for framing larger nebulae. You'll love the flat, colour-free field across a full-frame sensor and the forgiving 840mm focal length that doesn't punish every tracking hiccup. This isn't for you if you're chasing maximum resolution on small galaxies and planetary nebulae where the Askar's extra aperture and focal length would make a visible difference in your final stacks.
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 Askar 151PHQ is the scope most people will be using regularly six months from now. The Sky-Watcher Esprit 120ED rewards you more once you know what you're doing — it's worth revisiting after your first year.
Askar 151PHQ
View Askar 151PHQ →Sky-Watcher Esprit 120ED
View Sky-Watcher Esprit 120ED →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 151PHQ | Sky-Watcher Esprit 120ED |
|---|---|---|
Apertureⓘ The most important spec — bigger = more light = better views | 151mm | 120mm |
Focal Length Longer = more magnification potential | 1057mm | 840mm |
Focal Ratio Lower f-number = wider field of view; higher = more magnification per eyepiece | f/7 | 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 quintuplet with integrated field flattener | Fully multi-coated ED triplet with FMC on all air-to-glass surfaces |
How do you point it?
| Spec | Askar 151PHQ | Sky-Watcher Esprit 120ED |
|---|---|---|
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 151PHQ | Sky-Watcher Esprit 120ED |
|---|---|---|
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 151PHQ | Sky-Watcher Esprit 120ED |
|---|---|---|
OTA Weightⓘ Optical tube only — useful for comparing mount load capacity | 9.5kg | 5.7kg |
Tube Length | 800mm | 730mm |
Tube Material | Aluminium | Aluminium, white powder coat |
What's in the box?
| Spec | Askar 151PHQ | Sky-Watcher Esprit 120ED |
|---|---|---|
Diagonal Tilts the eyepiece 90° for comfortable viewing — useful on refractors |
Blue highlight: Askar 151PHQ advantage · Amber highlight: Sky-Watcher Esprit 120ED advantage · Greyed cells: equal or subjective.