Telescope Comparison
Celestron StarSense Explorer DX 102AZ vs Sky-Watcher Evostar 100ED
The Celestron StarSense Explorer DX 102AZ is a complete setup. The Sky-Watcher Evostar 100ED needs a mount before it's usable.
First light
Celestron · 102mm · £229
The simple alt-az visual scope
- 102mm refractor on a simple alt-az mount
- Good for: Moon, planets, bright open clusters
- No alignment required — quick to set up, intuitive to move
- Finding objects requires learning to star-hop: navigate with a finder scope and sky chart
- 7.5kg total — manageable to carry to dark-sky sites
Sky-Watcher · 100mm · £449
The custom-rig optical tube
- 100mm refractor — optical tube only, no mount included
- 900mm focal length at f/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
Celestron StarSense Explorer DX 102AZ 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
Sky-Watcher Evostar 100ED's longer focal length reaches higher magnification with the same eyepiece — better reach for planetary detail. Celestron StarSense Explorer DX 102AZ's shorter focal length gives a wider true field — better for large open clusters and extended nebulae.
Focal ratio
Celestron StarSense Explorer DX 102AZ's faster f/6.47 delivers wider fields with any eyepiece — better for open clusters and large nebulae. Sky-Watcher Evostar 100ED's f/9 provides more magnification per eyepiece — better for fine planetary detail.
Mount type
Sky-Watcher Evostar 100ED has no mount — add a compatible mount before you can observe. Celestron StarSense Explorer DX 102AZ is a complete ready-to-use system.
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 | Celestron StarSense Explorer DX 102AZ | Sky-Watcher Evostar 100ED |
|---|---|---|
| Planets | ||
| Moon | Excellent 102mm aperture delivers sharp crater detail, rilles, and mountain shadows; chromatic aberration adds a purple fringe at high power but doesn't obscure detail | Excellent 100mm aperture and f/9 focal ratio reward high magnification with sharp, high-contrast lunar detail |
| Saturn | Good Rings clearly defined at 100–130×, Cassini Division visible in steady seeing; 660mm focal length limits magnification headroom without a Barlow | Good 900mm focal length and clean ED optics show rings, Cassini Division in good seeing, and subtle disc banding |
| Jupiter | Good Two main cloud belts and Galilean moons easily seen; some chromatic aberration softens fine detail at higher magnifications | Good 100mm resolves two or more cloud belts, GRS, and moon shadow transits; f/9 handles high power well |
| Mars | Moderate Small orange disc visible at opposition with hints of the polar cap; 102mm aperture and 660mm focal length limit surface detail | Moderate Disc visible with polar cap and large albedo features at opposition, but 100mm limits fine surface detail |
Deep sky | ||
| Orion Nebula (M42) | Excellent 102mm gathers enough light for bright nebulosity and the Trapezium; 660mm focal length frames the full nebula extent well | Good Bright nebula core and trapezium well shown, but 900mm focal length crops the outer wings |
| Andromeda Galaxy (M31) | Excellent 660mm focal length captures the bright core and inner halo in a single field; 102mm aperture helps reveal outer structure from dark sites | Good Bright core and inner halo visible; 900mm frames only the central region, missing the full extent |
| Open clusters | Excellent 660mm focal length gives wide enough true fields to frame the Pleiades, Double Cluster, and other showpiece clusters | Good Compact clusters like M35 frame well; larger groups like the Double Cluster fill the low-power field |
| Globular clusters | Moderate M13 and M22 appear as bright, grainy balls; 102mm cannot resolve individual stars across the cluster | Moderate M13 and M5 appear granular at high power but the core remains unresolved at 100mm |
| Faint galaxies | Moderate Brighter Messier galaxies like M81/M82 visible as faint smudges; limited by 102mm light grasp | Moderate Brighter Messier galaxies detectable as smudges; 100mm lacks the aperture for structure or faint targets |
| Milky Way / wide field | Good 660mm focal length is slightly long for true sweeping panoramas but still delivers pleasant rich-field views of star clouds | Not recommended 900mm focal length produces too narrow a field for sweeping Milky Way star fields |
Other | ||
| Double stars | Excellent 102mm cleanly splits Albireo, Mizar, and wider doubles; close pairs below 1.5" are limited by chromatic aberration at f/6.5 | Excellent Clean ED optics at f/9 produce tight diffraction patterns; Dawes limit around 1.2 arcseconds |
The real tradeoff
Both scopes are capable. The question is which one fits the way you actually observe.
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The dark side
Every scope has a personality. Here’s where each one gets difficult.
Celestron
Celestron StarSense Explorer DX 102AZ
Chromatic aberration is baked into the f/6.5 achromatic design — expect persistent purple fringing on the Moon, Jupiter, and any bright star, which no accessory fully corrects.
The StarSense system depends on your smartphone's rear camera for plate-solving; older or budget phones may fail to lock on in light-polluted skies, leaving you with an expensive phone dock and no finder.
No tracking means every object drifts out of the field in under a minute at higher powers — you'll spend more time nudging the slightly stiff alt-az mount than actually observing at magnifications above 100×.
Sky-Watcher
Sky-Watcher Evostar 100ED
Sold as OTA only — no mount, diagonal, finder, or eyepieces are included, so the £449 price tag is just the starting point and total observing cost is significantly higher.
At 900mm f/9, deep-sky imaging requires long exposures even with a tracking mount, and the field is too narrow for wide-field work without a dedicated reducer.
The tube weighs approximately 4.4 kg before accessories, so you'll need at least a mid-range equatorial mount for stable imaging — a lightweight alt-az or photo tripod won't cut it.
Which is right for you?
Two different buyers. Two different right answers.
The simple alt-az visual scope
Celestron · Celestron StarSense Explorer DX 102AZ
You're new to astronomy, you don't know Betelgeuse from Bellatrix, and you want to actually find things on your first night out. You'll love unboxing a complete, ready-to-observe kit at £229 that uses your phone to guide you across the sky — no alignment procedures, no star charts, no prior knowledge required. This is your scope if you value breadth of discovery over optical perfection, and you're happy accepting some purple fringing and manual tracking as the trade-off for an absurdly low barrier to entry. This isn't for you if you already know the sky well enough to find targets on your own, or if you're planning to grow into astrophotography — there's no tracking, no equatorial mount, and no upgrade path beyond phone snapshots of the Moon.
The custom-rig optical tube
Sky-Watcher · Sky-Watcher Evostar 100ED
You already own a decent equatorial mount — or you're ready to invest in one — and you want the sharpest possible planetary and lunar views from a portable refractor. You'll love the Evostar 100ED if you're the kind of observer who spends twenty minutes on Jupiter chasing festoons and the GRS, or who splits tight double stars for sport, because the ED glass at f/9 delivers a level of contrast and colour correction the StarSense achromat simply can't match. This isn't for you if you need a ready-to-observe package out of the box — you'll be sourcing a mount, diagonal, finder, and eyepieces before you see a single photon, and the total spend will be roughly triple the StarSense's price.
Our verdict
This comparison has a catch: the Sky-Watcher Evostar 100ED is a bare optical tube. You cannot use it without a separate mount — which adds meaningful cost and complexity. The Celestron StarSense Explorer DX 102AZ is a complete, ready-to-observe package.
For most buyers, the Celestron StarSense Explorer DX 102AZ is the right choice — you can observe the same night it arrives. The Sky-Watcher Evostar 100ED makes sense if you already own a compatible mount, or are deliberately building a specific imaging setup piece by piece. If I had to choose for a first telescope: the Celestron StarSense Explorer DX 102AZ, without hesitation.
Celestron StarSense Explorer DX 102AZ
View Celestron StarSense Explorer DX 102AZ →Sky-Watcher Evostar 100ED
View Sky-Watcher Evostar 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 | Celestron StarSense Explorer DX 102AZ | Sky-Watcher Evostar 100ED |
|---|---|---|
Apertureⓘ The most important spec — bigger = more light = better views | 102mm | 100mm |
Focal Length Longer = more magnification potential | 660mm | 900mm |
Focal Ratio Lower f-number = wider field of view; higher = more magnification per eyepiece | f/6.47 | f/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 achromatic refractor | Fully multi-coated ED doublet |
How do you point it?
| Spec | Celestron StarSense Explorer DX 102AZ | Sky-Watcher Evostar 100ED |
|---|---|---|
Mount Type The mechanical system that holds and moves the telescope | Alt-Az | 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 | Celestron StarSense Explorer DX 102AZ | Sky-Watcher Evostar 100ED |
|---|---|---|
Focuser Size 2" accepts wider eyepieces and gives better low-power views | 1.25" | 2" |
Focuser Type Rack-and-pinion is standard; Crayford and dual-speed are smoother | Rack and pinion | Dual-speed Crayford (with 1.25" adapter) |
Size & weight
| Spec | Celestron StarSense Explorer DX 102AZ | Sky-Watcher Evostar 100ED |
|---|---|---|
OTA Weightⓘ Optical tube only — useful for comparing mount load capacity | 3.2kg | 2.6kg |
Total Weight Full setup including mount — this is what you lug to the car | 7.5kg | — |
Tube Length | 660mm | 720mm |
Tube Material | Aluminium | Aluminium |
What's in the box?
| Spec | Celestron StarSense Explorer DX 102AZ | Sky-Watcher Evostar 100ED |
|---|---|---|
Eyepieces Included eyepieces — more is better, but quality matters more than quantity | 25mm and 10mm Kellner | — |
Finder Scope Helps you locate areas of the sky before switching to the main eyepiece | StarSense sky recognition dock (uses your smartphone) | — |
Diagonalⓘ Tilts the eyepiece 90° for comfortable viewing — useful on refractors |
Blue highlight: Celestron StarSense Explorer DX 102AZ advantage · Amber highlight: Sky-Watcher Evostar 100ED advantage · Greyed cells: equal or subjective.