Telescope Comparison
Bresser Messier 10" Dobsonian vs Bresser Messier 12" Dobsonian
305mm versus 254mm — the aperture difference is the comparison.
First light
Bresser · 254mm · £499
The maximum-aperture visual reflector
- 254mm Newtonian on a floor-standing Dobsonian alt-az rocker box
- Good for: full visual programme — planets, Moon, globular clusters, galaxies, nebulae
- No alignment required — set up and observe in under 10 minutes
- No motorised tracking — targets drift at high magnification as Earth rotates
- 27kg total — designed for a fixed garden or regular dark-sky site, not casual transport
Bresser · 305mm · £699
The maximum-aperture visual reflector
- 305mm Newtonian on a floor-standing Dobsonian alt-az rocker box
- Good for: full visual programme — planets, Moon, globular clusters, galaxies, nebulae
- No alignment required — set up and observe in under 10 minutes
- No motorised tracking — targets drift at high magnification as Earth rotates
- 42kg total — designed for a fixed garden or regular dark-sky site, not casual transport
The full picture
The numbers that separate these two scopes — and what they mean at the eyepiece.
Aperture
Bresser Messier 12" Dobsonian gathers 1.4× 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
Bresser Messier 12" Dobsonian's longer focal length reaches higher magnification with the same eyepiece — better reach for planetary detail. Bresser Messier 10" Dobsonian'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
Same mount type — setup experience and ergonomics will be similar. Differences lie in build quality and included accessories.
Weight (OTA)
Bresser Messier 10" Dobsonian's optical tube is 9.0kg lighter. Relevant if you plan to use it on multiple mounts or carry the tube to dark-sky sites separately.
Optical design
Same optical design — differences between these scopes come from aperture, mount, and focal ratio.
At the eyepiece
| Target | Bresser Messier 10" Dobsonian | Bresser Messier 12" Dobsonian |
|---|---|---|
| Planets | ||
| Moon | Excellent 254mm resolves sub-kilometre crater detail; the terminator is spectacular with hundreds of features visible per session | Excellent 305mm aperture delivers overwhelming detail — craterlets, rilles, and shadow play at 200–300×; a neutral density filter helps manage brightness |
| Saturn | Excellent Cassini Division cleanly split, cloud banding on the globe visible, and multiple moons in the field at 1270mm focal length | Excellent Cassini Division easily visible, Crepe Ring and cloud banding on the disc accessible in steady seeing at 250×+ |
| Jupiter | Excellent Multiple cloud belts, festoons, GRS detail, and moon shadow transits all accessible at 200x+ in steady seeing | Excellent Multiple cloud belts, festoons, the Great Red Spot, and moon shadow transits visible; 1525mm focal length supports high magnification well |
| Mars | Excellent 254mm aperture and 1270mm focal length (extendable with Barlows to 2500mm+) reveal dark albedo features, polar caps, and limb phenomena at opposition | Excellent At 305mm and 1525mm focal length, dark albedo features, polar caps, and occasional dust storm effects visible near opposition |
Deep sky | ||
| Orion Nebula (M42) | Excellent Bright nebulosity fills the field with structure and hints of colour; the Trapezium cluster is cleanly resolved into four or more stars | Excellent Trapezium cleanly split, extensive nebulosity with hints of colour; 1525mm focal length crops the widest extent but detail is superb |
| Andromeda Galaxy (M31) | Good 1270mm focal length captures the bright core and inner disc well but crops the full 3° extent; dust lanes visible with averted vision | Moderate 1525mm focal length shows only the bright core and inner disc — too narrow to frame the full 3° extent; dust lanes visible but outer halo is cropped |
| Open clusters | Good 1270mm focal length means larger clusters like the Double Cluster just fit the field with a wide-angle 2-inch eyepiece; compact clusters like M37 are stunning | Moderate 1525mm focal length means larger clusters like the Double Cluster overfill the field; compact clusters like M37 are well-served |
| Globular clusters | Excellent 254mm resolves individual stars across the face of M13, M3, and M92 — not just at the edges but into the core region | Excellent 305mm resolves individual stars across the core of M13, M3, and M5 — one of this scope's signature strengths |
| Faint galaxies | Excellent Spiral arms in M51, dust lanes in M82, and structure in dozens of NGC galaxies become accessible under dark skies | Excellent 305mm pulls in galaxies to mag 14+; spiral arm structure visible in M51, NGC 891's dust lane detectable from dark sites |
| Milky Way / wide field | Moderate 1270mm focal length limits the true field even with a 2-inch eyepiece; individual star clouds are impressive but you cannot sweep wide swathes | Not recommended 1525mm focal length gives far too narrow a field for sweeping star fields — a separate wide-field instrument is needed |
Other | ||
| Double stars | Excellent 254mm gives a Dawes limit around 0.46 arcseconds — tight pairs like Porrima and Castor are cleanly split; f/5 may show slight diffraction effects vs longer focal ratios | Excellent 305mm resolves pairs under 0.5 arcsecond; f/5 is faster than ideal for tight doubles but a Barlow sharpens the Airy disc at high power |
| Astrophotography (deep sky) | Not recommended Manual Dobsonian mount provides no tracking — long-exposure imaging is not possible without aftermarket equatorial platform | Not recommended Manual Dobsonian mount has no tracking — long exposures are not possible |
| Astrophotography (planetary) | Challenging Short video captures of bright planets are possible with a webcam, but manual tracking at 200x+ is very difficult and results are inconsistent | Moderate Lucky imaging with a high-speed camera is technically possible at 305mm, but manual tracking makes it difficult to keep targets centred; results are inconsistent |
The real tradeoff
Both scopes are capable. The question is which one fits the way you actually observe.
Bresser Messier 10" Dobsonian
- You'll wrestle about 25kg out of the car instead of 42kg — that difference matters at 11pm in a muddy field, and it's the reason the 10" actually gets used on weeknights when the 12" would stay in the garage.
- You'll still resolve spiral arms in M51 and individual stars across M13's core — you're giving up the faintest galaxy-group members and some fine nebula filament detail, not the fundamental deep-sky experience.
- You'll spend £200 less on the scope itself, which is exactly the budget for a coma corrector, a decent 2" wide-field eyepiece, and a laser collimator — accessories both scopes desperately need but neither includes.
Bresser Messier 12" Dobsonian
- You'll collect 44% more light than the 10", and on faint targets like Virgo Cluster galaxies or Veil Nebula filaments, that's the difference between 'I think I see something' and 'there it is' — but only if you actually get the scope to a dark site.
- You'll need a second pair of hands or a strong back to move 42kg of telescope — if you hesitate even slightly at the thought of solo-loading this into a car, you'll observe less often than you would with the lighter 10".
- You'll wait 30–60 minutes for the 12" mirror to cool down before it delivers sharp views, so your sessions need to be planned events, not spontaneous half-hour peeks — factor that into every outing.
The dark side
Every scope has a personality. Here’s where each one gets difficult.
Bresser
Bresser Messier 10" Dobsonian
At ~1.2 metres long and 25kg assembled, you'll still need rear seats down or an estate car — this is not a small telescope, even if it's manageable next to the 12".
The included 25mm Super Plössl is a placeholder, not a serious eyepiece — budget for at least a 2" wide-field and a quality short-focal-length eyepiece, plus a coma corrector to tame the f/5 edge distortion.
No tracking means you're nudging the base every few seconds at 200×+ on planets — extended planetary observation is an exercise in patience, not relaxation.
Bresser
Bresser Messier 12" Dobsonian
42kg total weight makes solo transport genuinely difficult — this is a two-trip, two-person, big-car telescope, and underestimating that will cost you observing nights.
The f/5 coma eats the outer 30% of your field with wide-angle eyepieces, so a coma corrector isn't optional — it's essential, and it's an added cost on top of the £699 price tag.
Substantial cool-down time means you can lose up to an hour of a short winter session just waiting for thermal equilibrium — arrive early or accept soft views at the start of every outing.
Which is right for you?
Two different buyers. Two different right answers.
The maximum-aperture visual reflector
Bresser · Bresser Messier 10" Dobsonian
You're stepping up from a smaller scope and you want to see genuine structure in deep-sky objects — spiral arms, resolved globular cores, nebula detail — without committing to a telescope that dominates your storage space and needs a helper to move. You'd rather spend the £200 savings on the eyepieces and accessories that both scopes need, and you value actually getting out observing over squeezing out the last fraction of faint-target detail. If you observe alone and drive a normal-sized car, this is the scope that will actually come with you.
The maximum-aperture visual reflector
Bresser · Bresser Messier 12" Dobsonian
You're chasing the faintest targets — galaxy groups, delicate nebula filaments through narrowband filters, the deep resolved cores of distant globulars — and you know that no amount of eyepiece upgrades can substitute for raw aperture. You have the vehicle space, the physical willingness to handle 42kg regularly, and the patience for 30–60 minutes of cool-down before your session starts. If you've already owned a smaller scope and found yourself wishing for 'just a bit more light,' this is the answer — but only if you're honest with yourself about the logistics, because a 12" Dob that stays home loses to a 10" that gets used.
Our verdict
At £499 versus £699, the Bresser Messier 12" Dobsonian costs 40% more. It delivers 51mm more aperture — a real and visible advantage on faint targets.
If budget is a genuine constraint, the Bresser Messier 10" Dobsonian will make you a happy observer. The Bresser Messier 12" Dobsonian's optical advantage on faint targets is real and you are unlikely to regret it if you can stretch. If I had to choose without knowing your situation: start with the Bresser Messier 10" Dobsonian, use it for a year, then upgrade knowing exactly what you want.
Bresser Messier 10" Dobsonian
View Bresser Messier 10" Dobsonian →Bresser Messier 12" Dobsonian
View Bresser Messier 12" Dobsonian →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 | Bresser Messier 10" Dobsonian | Bresser Messier 12" Dobsonian |
|---|---|---|
Apertureⓘ The most important spec — bigger = more light = better views | 254mm | 305mm |
Focal Length Longer = more magnification potential | 1270mm | 1525mm |
Focal Ratio Lower f-number = wider field of view; higher = more magnification per eyepiece | f/5 | f/5 |
Optical Design The type of optics — each design has different strengths | Dobsonian | Dobsonian |
Coatings Better coatings = more light transmission through the optics | Parabolic primary mirror, fully coated | Parabolic primary mirror, fully coated |
How do you point it?
| Spec | Bresser Messier 10" Dobsonian | Bresser Messier 12" Dobsonian |
|---|---|---|
Mount Type The mechanical system that holds and moves the telescope | Dobsonian | Dobsonian |
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 | Bresser Messier 10" Dobsonian | Bresser Messier 12" Dobsonian |
|---|---|---|
Focuser Size 2" accepts wider eyepieces and gives better low-power views | 2" | 2" |
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" with 1.25" adapter) |
Size & weight
| Spec | Bresser Messier 10" Dobsonian | Bresser Messier 12" Dobsonian |
|---|---|---|
OTA Weightⓘ Optical tube only — useful for comparing mount load capacity | 18kg | 27kg |
Total Weightⓘ Full setup including mount — this is what you lug to the car | 27kg | 42kg |
Tube Length | 1270mm | 1525mm |
Tube Material | Steel | Steel |
What's in the box?
| Spec | Bresser Messier 10" Dobsonian | Bresser Messier 12" Dobsonian |
|---|---|---|
Eyepieces Included eyepieces — more is better, but quality matters more than quantity | 25mm and 10mm eyepieces | 25mm and 10mm eyepieces |
Finder Scope Helps you locate areas of the sky before switching to the main eyepiece | 8x50 right-angle finder | 8x50 right-angle finder |
Diagonal Tilts the eyepiece 90° for comfortable viewing — useful on refractors |
Blue highlight: Bresser Messier 10" Dobsonian advantage · Amber highlight: Bresser Messier 12" Dobsonian advantage · Greyed cells: equal or subjective.