Telescope Comparison
Orion StarBlast 6 Astro Reflector vs Ursa Major 6" f/8 Planetary Dobsonian
Same optics. Different mount philosophy.
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First light
Orion · 150mm
The simple alt-az visual scope
- 150mm newtonian reflector 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
- 5.4kg total — manageable to carry to dark-sky sites
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. Orion StarBlast 6 Astro Reflector's shorter focal length gives a wider true field — better for large open clusters and extended nebulae.
Focal ratio
Orion StarBlast 6 Astro Reflector'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
Both are alt-az in principle, but the Dobsonian rocker-box is typically more stable at the eyepiece. Neither scope tracks — objects drift at high magnification.
Weight (OTA)
Orion StarBlast 6 Astro Reflector's optical tube is 3.6kg lighter. Relevant if you plan to use it on multiple mounts or carry the tube to dark-sky sites separately.
Optical design
Orion StarBlast 6 Astro Reflector 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.
Both scopes are solving a similar problem in a similar way. The differences are real — mount type and setup experience — but these show up after several months of regular use, not on the first night. Pick the one whose design best matches how you actually plan to observe.
The dark side
Every scope has a personality. Here’s where each one gets difficult.
Orion
Orion StarBlast 6 Astro Reflector
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.
Finding faint objects from a light-polluted garden is genuinely hard
Star-hopping to a globular cluster or dim galaxy from a suburban sky requires learning. Users report a real demoralising phase in the first weeks — landing on the wrong star field, convincing yourself it's the target, then finding out later it wasn't. This improves rapidly with experience.
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 simple alt-az visual scope
Orion · Orion StarBlast 6 Astro Reflector
You’ll love this if…
- You want the fastest possible setup — no alignment, no polar alignment, just point and look
- Learning the sky by star-hopping feels like part of the appeal, not a barrier to it
- Portability matters — this mount is manageable to carry to a dark-sky site without a car full of equipment
This will frustrate you if…
- 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
- You try to find faint objects from a light-polluted garden and mostly fail — users report a real demoralising phase in the first weeks of star-hopping that improves quickly but is genuinely discouraging at the start
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
At similar price points, these scopes offer different amounts of aperture per pound. The Orion StarBlast 6 Astro Reflector gives you more light-gathering for your money — and for visual observing, aperture per pound is the most useful single metric.
For pure optical value, the Orion StarBlast 6 Astro Reflector is the stronger pick. The Ursa Major 6" f/8 Planetary Dobsonian compensates with other features — decide whether those trade-offs justify the premium. If I had to choose: the Orion StarBlast 6 Astro Reflector — more aperture per pound means more sky.
Orion StarBlast 6 Astro Reflector
View Orion StarBlast 6 Astro Reflector →Ursa Major 6" f/8 Planetary Dobsonian
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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 | Orion StarBlast 6 Astro Reflector | 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 | 94% reflectivity parabolic primary mirror | — |
How do you point it?
| Spec | Orion StarBlast 6 Astro Reflector | Ursa Major 6" f/8 Planetary Dobsonian |
|---|---|---|
Mount Type The mechanical system that holds and moves the telescope | Alt-Az | 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 | Orion StarBlast 6 Astro Reflector | Ursa Major 6" f/8 Planetary Dobsonian |
|---|---|---|
Focuser Size 2" accepts wider eyepieces and gives better low-power views | 1.25" | 1.25" |
Focuser Type Rack-and-pinion is standard; Crayford and dual-speed are smoother | Rack and pinion | 1.25" CNC Crayford |
Size & weight
| Spec | Orion StarBlast 6 Astro Reflector | Ursa Major 6" f/8 Planetary Dobsonian |
|---|---|---|
OTA Weightⓘ Optical tube only — useful for comparing mount load capacity | 5.4kg | 9kg |
Total Weightⓘ Full setup including mount — this is what you lug to the car | 5.4kg | 20.9kg |
Tube Length | 635mm | 1100mm |
Tube Material | Steel | — |
What's in the box?
| Spec | Orion StarBlast 6 Astro Reflector | Ursa Major 6" f/8 Planetary Dobsonian |
|---|---|---|
Eyepieces Included eyepieces — more is better, but quality matters more than quantity | 25mm and 10mm Sirius Plössl | 9mm and 25mm 1.25" Super-Plössl |
Finder Scope Helps you locate areas of the sky before switching to the main eyepiece | EZ Finder II red dot | 6x30 straight-through |
Diagonalⓘ Tilts the eyepiece 90° for comfortable viewing — useful on refractors | — |
Blue highlight: Orion StarBlast 6 Astro Reflector advantage · Amber highlight: Ursa Major 6" f/8 Planetary Dobsonian advantage · Greyed cells: equal or subjective.