Telescope Comparison
Bresser Messier N-150/750 vs Ursa Major 6" f/8 Planetary Dobsonian
Same optics. Different mount philosophy.
Affiliate links — we earn from qualifying purchases at no extra cost to you.
First light
Bresser · 150mm · £229
The sky-learner's equatorial scope
- 150mm newtonian reflector on a manual equatorial mount
- Good for: Moon, planets, bright star clusters and nebulae
- Setup includes rough polar alignment before observing — more steps than a simple alt-az
- Mount axes feel counterintuitive at first; users find they become natural after several sessions
- Keeps the door open for adding tracking motors and moving into astrophotography later
Ursa Major · 152mm · £269
The maximum-aperture visual reflector
- 152mm 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
- 20.9kg 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
Effectively equal light-gathering. Aperture won't settle this comparison — the mount, focal ratio, and observing experience are what differ.
Focal length
Ursa Major 6" f/8 Planetary Dobsonian's longer focal length reaches higher magnification with the same eyepiece — better reach for planetary detail. Bresser Messier N-150/750's shorter focal length gives a wider true field — better for large open clusters and extended nebulae.
Focal ratio
Bresser Messier N-150/750's faster f/5 delivers wider fields with any eyepiece — better for open clusters and large nebulae. Ursa Major 6" f/8 Planetary Dobsonian's f/7.9 provides more magnification per eyepiece — better for fine planetary detail.
Mount type
Ursa Major 6" f/8 Planetary Dobsonian's Dobsonian is immediately intuitive — no alignment, push to aim, observe. Bresser Messier N-150/750's equatorial mount requires polar alignment before each session but tracks the sky as Earth rotates, keeping objects centred.
Weight (OTA)
Bresser Messier N-150/750's optical tube is 4.0kg lighter. Relevant if you plan to use it on multiple mounts or carry the tube to dark-sky sites separately.
Optical design
Bresser Messier N-150/750 is a Newtonian reflector (mirrors, needs occasional collimation); Ursa Major 6" f/8 Planetary Dobsonian is a DOBSONIAN. Different optical formulas produce different strengths — reflectors give more aperture per pound; refractors give sharper contrast and require no collimation.
At the eyepiece
Both scopes · same aperture
Both are 151mm Newtonian reflectors — light gathering is identical. What you see through each depends on your eyepieces, your sky, and the steadiness of the atmosphere, not which scope you bought. Saturn's rings separate clearly from the disk; in good seeing, the Cassini Division — the dark gap between the A and B rings — is a genuine target at moderate magnification. Jupiter shows two equatorial cloud bands reliably, four Galilean moons changing position night to night. The Orion Nebula (M42) shows real nebulosity around the Trapezium, which splits into four stars at moderate magnification. The Andromeda Galaxy (M31) fills a wide-field eyepiece, the bright core distinct from the outer halo. What separates these scopes is the mount, the setup experience, and where you can use them — not what you see through them.
The real tradeoff
Both scopes are capable. The question is which one fits the way you actually observe.
For visual observing, the Ursa Major 6" f/8 Planetary Dobsonian's Dobsonian mount is simpler — no alignment, push to aim. The Bresser Messier N-150/750's equatorial mount has a learning curve but tracks the sky as Earth rotates, keeping objects centred at high magnification. If astrophotography is where you're eventually headed, the equatorial mount is the right foundation. For visual observing only, the Dobsonian is usually the easier starting point.
The dark side
Every scope has a personality. Here’s where each one gets difficult.
Bresser
Bresser Messier N-150/750
Mount axes feel counterintuitive at first
An equatorial mount does not move up/down and left/right as you expect — it follows the rotation of the sky. Users consistently report that it takes several sessions before it begins to feel natural.
Collimation: the skill nobody mentions in the listing
The mirrors go out of alignment with use. Stars look bloated rather than sharp when this happens. Users report that a Cheshire eyepiece makes collimation straightforward once learned, but most beginners don't discover they need it until their second or third month.
Ursa Major
Ursa Major 6" f/8 Planetary Dobsonian
Objects drift out of view at high magnification
There is no tracking. At high magnification, targets drift across the field as Earth rotates and require regular manual nudging to keep them centred.
Too large for spontaneous outings
At 20.9kg total, getting this scope to a dark-sky site requires planning and ideally a second pair of hands. It suits a fixed garden setup or a dedicated trip, not an impulsive clear-night dash.
Which is right for you?
Two different buyers. Two different right answers.
The sky-learner's equatorial scope
Bresser · Bresser Messier N-150/750
You’ll love this if…
- You want to understand how an equatorial mount works — and you're prepared to spend a few sessions on polar alignment before it becomes second nature
- You plan to observe from a fixed spot in the garden, where the mount can stay roughly polar-aligned between sessions
- Astrophotography is on your radar even if you're not starting there — this mount keeps that option open with a motor drive upgrade
This will frustrate you if…
- You find the equatorial mount's axes feel wrong — objects move in unexpected directions and polar alignment adds a step each session that takes several outings to become automatic
- You notice that stars look bloated rather than sharp and don't know why — users report this is usually a collimation issue that's straightforward to fix once you know about it, but the listing doesn't mention it
The maximum-aperture visual reflector
Ursa Major · Ursa Major 6" f/8 Planetary Dobsonian
You’ll love this if…
- More aperture per pound is your main criterion — this design gives more light-gathering for your money than any other mount type at this price
- You plan to observe from a fixed garden or regular dark-sky site where you can set it up and leave it between sessions
- You prefer manual navigation — the Dobsonian rewards patient, hands-on observing and builds genuine sky knowledge over time
This will frustrate you if…
- You want to observe at high magnification without nudging the scope constantly — there is no tracking, and targets drift across the field as Earth rotates
- You want to take it to different locations easily — at this weight and size, it's a significant lift and benefits from a second pair of hands
- You want to take it out for spontaneous sessions — at this weight, getting it in and out of a car on your own requires planning and ideally a second pair of hands
Our verdict
Same aperture, same light-gathering, £40 price difference. The extra cost of the Ursa Major 6" f/8 Planetary Dobsonian buys a different mount — not better optics.
For most beginners, the Bresser Messier N-150/750 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 Ursa Major 6" f/8 Planetary Dobsonian makes sense if the mount it comes with is specifically what you want to learn. If I had to choose: the Bresser Messier N-150/750 — same sky, less money.
Bresser Messier N-150/750
View Bresser Messier N-150/750 →Ursa Major 6" f/8 Planetary Dobsonian
View Ursa Major 6" f/8 Planetary Dobsonian →Affiliate links — we earn from qualifying purchases at no extra cost to you.
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 N-150/750 | Ursa Major 6" f/8 Planetary Dobsonian |
|---|---|---|
Apertureⓘ The most important spec — bigger = more light = better views | 150mm | 152mm |
Focal Length Longer = more magnification potential | 750mm | 1200mm |
Focal Ratio Lower f-number = wider field of view; higher = more magnification per eyepiece | f/5 | f/7.9 |
Optical Design The type of optics — each design has different strengths | Newtonian Reflector | Dobsonian |
Coatings Better coatings = more light transmission through the optics | Parabolic primary mirror, fully coated | — |
How do you point it?
| Spec | Bresser Messier N-150/750 | Ursa Major 6" f/8 Planetary Dobsonian |
|---|---|---|
Mount Type The mechanical system that holds and moves the telescope | Equatorial | 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 N-150/750 | Ursa Major 6" f/8 Planetary Dobsonian |
|---|---|---|
Focuser Size 2" accepts wider eyepieces and gives better low-power views | 2" | 1.25" |
Focuser Type Rack-and-pinion is standard; Crayford and dual-speed are smoother | Dual-speed Crayford (2" with 1.25" adapter) | 1.25" CNC Crayford |
Size & weight
| Spec | Bresser Messier N-150/750 | Ursa Major 6" f/8 Planetary Dobsonian |
|---|---|---|
OTA Weightⓘ Optical tube only — useful for comparing mount load capacity | 5kg | 9kg |
Total Weightⓘ Full setup including mount — this is what you lug to the car | 13.5kg | 20.9kg |
Tube Length | 670mm | 1100mm |
Tube Material | Steel | — |
What's in the box?
| Spec | Bresser Messier N-150/750 | Ursa Major 6" f/8 Planetary Dobsonian |
|---|---|---|
Eyepieces Included eyepieces — more is better, but quality matters more than quantity | 25mm and 10mm eyepieces | 9mm and 25mm 1.25" Super-Plössl |
Finder Scope Helps you locate areas of the sky before switching to the main eyepiece | 8x50 optical finder | 6x30 straight-through |
Diagonalⓘ Tilts the eyepiece 90° for comfortable viewing — useful on refractors | — |
Blue highlight: Bresser Messier N-150/750 advantage · Amber highlight: Ursa Major 6" f/8 Planetary Dobsonian advantage · Greyed cells: equal or subjective.