Telescope Comparison
StellaLyra 8" f/5 Newtonian OTA vs Ursa Major 6" f/8 Planetary Dobsonian
The Ursa Major 6" f/8 Planetary Dobsonian is a complete setup. The StellaLyra 8" f/5 Newtonian OTA needs a mount before it's usable.
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First light
StellaLyra · 200mm · £469
The custom-rig optical tube
- 200mm newtonian reflector — optical tube only, no mount included
- 1000mm focal length at f/5
- 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
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
StellaLyra 8" f/5 Newtonian OTA gathers 1.7× 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
Ursa Major 6" f/8 Planetary Dobsonian's longer focal length reaches higher magnification with the same eyepiece — better reach for planetary detail. StellaLyra 8" f/5 Newtonian OTA's shorter focal length gives a wider true field — better for large open clusters and extended nebulae.
Focal ratio
StellaLyra 8" f/5 Newtonian OTA'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
StellaLyra 8" f/5 Newtonian OTA has no mount — add a compatible mount before you can observe. Ursa Major 6" f/8 Planetary Dobsonian 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
StellaLyra 8" f/5 Newtonian OTA 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
StellaLyra
StellaLyra 8" f/5 Newtonian OTA
The Moon fills the field at low power with more detail than you'll have time to explore on any given night. Saturn's rings are unmistakable from the first session; in good seeing, the Cassini Division — the dark gap between the A and B rings — is a genuine target at higher magnification. Jupiter shows two equatorial cloud bands clearly, the four Galilean moons changing position night to night. The Orion Nebula (M42) shows wide nebulosity with the Trapezium splitting cleanly into four points at 80×. The Hercules Cluster (M13) begins to resolve into individual stars at the outer edges at higher magnification. The Andromeda Galaxy (M31) fills a wide-field eyepiece; the bright core and inner disc are obvious, and on a dark night the dust lane becomes visible with careful looking. The StellaLyra 8" f/5 Newtonian OTA gathers 1.7× more light than the Ursa Major 6" f/8 Planetary Dobsonian — a difference that's marginal on bright targets but visible on fainter ones: dimmer galaxies, faint globular clusters, and extended nebulosity that sits below the threshold of the smaller aperture.
Ursa Major
Ursa Major 6" f/8 Planetary Dobsonian
The Moon fills the field at low power with more detail than you'll have time to explore on any given night. Saturn's rings are unmistakable from the first session; in good seeing, the Cassini Division — the dark gap between the A and B rings — is a genuine target at higher magnification. Jupiter shows two equatorial cloud bands clearly, the four Galilean moons changing position night to night. The Orion Nebula (M42) shows clear structure — nebulosity spreading around the Trapezium, which splits at moderate power. The Andromeda Galaxy (M31) shows a concentrated core clearly. The Hercules Cluster (M13) shows some resolution at the edges at higher magnification.
The real tradeoff
Both scopes are capable. The question is which one fits the way you actually observe.
The Ursa Major 6" f/8 Planetary Dobsonian is a complete package — everything arrives in one box and you can observe the same day. The StellaLyra 8" f/5 Newtonian OTA is a bare optical tube that needs a separate compatible mount before you can point it at anything, adding significant cost and complexity. Unless you already own a suitable mount, the Ursa Major 6" f/8 Planetary Dobsonian is the practical choice.
The dark side
Every scope has a personality. Here’s where each one gets difficult.
StellaLyra
StellaLyra 8" f/5 Newtonian OTA
No mount included
You cannot observe until you buy a separate compatible mount — add at least £100–300 before you have a working telescope.
Nothing to look through on day one
Until a mount arrives, the optical tube is a piece of glass you cannot point at the sky.
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 custom-rig optical tube
StellaLyra · StellaLyra 8" f/5 Newtonian OTA
You’ll love this if…
- You already own a compatible equatorial or alt-az mount — this is the optical tube you've specifically chosen to put on it
- You're building an imaging rig piece by piece and know exactly what you need at the end of a focuser
- Choosing an optical tube independently of the mount gives you more flexibility over your overall system
This will frustrate you if…
- You buy it without fully accounting for the mount — add at least £100–300 to the purchase price before you have a working telescope
- You expected a complete package and didn't realise this is a bare optical tube that cannot be used without a separate mount
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
This comparison has a catch: the StellaLyra 8" f/5 Newtonian OTA is a bare optical tube. You cannot use it without a separate mount — which adds meaningful cost and complexity. The Ursa Major 6" f/8 Planetary Dobsonian is a complete, ready-to-observe package.
For most buyers, the Ursa Major 6" f/8 Planetary Dobsonian is the right choice — you can observe the same night it arrives. The StellaLyra 8" f/5 Newtonian OTA 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 Ursa Major 6" f/8 Planetary Dobsonian, without hesitation.
StellaLyra 8" f/5 Newtonian OTA
View StellaLyra 8" f/5 Newtonian OTA →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 | StellaLyra 8" f/5 Newtonian OTA | Ursa Major 6" f/8 Planetary Dobsonian |
|---|---|---|
Apertureⓘ The most important spec — bigger = more light = better views | 200mm | 152mm |
Focal Length Longer = more magnification potential | 1000mm | 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 |
How do you point it?
| Spec | StellaLyra 8" f/5 Newtonian OTA | Ursa Major 6" f/8 Planetary Dobsonian |
|---|---|---|
Mount Type The mechanical system that holds and moves the telescope | None (OTA only) | 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 | StellaLyra 8" f/5 Newtonian OTA | 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 | 2" dual-speed linear bearing Crayford | 1.25" CNC Crayford |
Size & weight
| Spec | StellaLyra 8" f/5 Newtonian OTA | Ursa Major 6" f/8 Planetary Dobsonian |
|---|---|---|
OTA Weight Optical tube only — useful for comparing mount load capacity | 9kg | 9kg |
Total Weight Full setup including mount — this is what you lug to the car | — | 20.9kg |
Tube Length | 900mm | 1100mm |
What's in the box?
| Spec | StellaLyra 8" f/5 Newtonian OTA | Ursa Major 6" f/8 Planetary Dobsonian |
|---|---|---|
Eyepieces Included eyepieces — more is better, but quality matters more than quantity | — | 9mm and 25mm 1.25" Super-Plössl |
Finder Scope Helps you locate areas of the sky before switching to the main eyepiece | 8x50 straight-through multicoated | 6x30 straight-through |
Blue highlight: StellaLyra 8" f/5 Newtonian OTA advantage · Amber highlight: Ursa Major 6" f/8 Planetary Dobsonian advantage · Greyed cells: equal or subjective.