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Buy the right telescope, not the biggest one

300×
Saturn at 300× in 300 mm — exit pupil 1.0 mm, Bortle 6 sky. Computed, not photographed.

250–300 mm Dobsonian

GSO Dobson 300/1500

Where galaxies start having structure and planetary nebulae start having colour. Also where an instrument starts needing a plan rather than a decision.

€899seen 23 Oct 2026 at Astroshop

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One email when the price we observe for the GSO Dobson 300/1500 falls at least 5% below the lowest we observed in the previous 30 days. At most one a week.

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  • 300 mmAperture
  • f/5.0Focal ratio
  • 33 kgTypical weight
  • 50–600×Useful magnification

Should you buy it?

  • Yes if what you mainly want is nebulae, clusters and galaxies, by eye, the moon and the planets: that is what this family does best.
  • No if your priority is learn my way around the sky, taking it with me: other families do better for the same money.
  • 33 kg: you need to be able to carry it outside, every night, unaided.

Computed from its family's per-goal scores and its own numbers — not a rating, not one evening's opinion.

Where to buy

Also search at First Light Optics · Optique Unterlinden · Pierro Astro · Teleskop-Express (searches; neither price nor stock checked)

1 of these 5 links earn us a commission, marked above. Sorted by price, never by what pays. How this site is funded.

Prices are observed on the date shown, never live. Links marked earn us a commission and cost you nothing extra.

Observed price history

Unchanged at Astroshop: €899 at each of the 25 readings from 29 Sept 2026 to 23 Oct 2026.

Only prices actually read on the retailer’s page, one per day at most; a day without a reading is a gap, not a guess.

Every tracked model on one page: the price observatory →

What it shows, really

These circles are simulations, computed from the aperture, the magnification and the sky — indicative, not exact. A real night also depends on the turbulence, your eyes and your experience. Closer to the truth than the photo on the box; still not a promise.

Under a suburban sky (Bortle 6), through a common 25 mm eyepiece for wide targets and a 10 mm for planets. Every circle is the true field — nothing is enlarged.

The Moon60× · 300 mm 5.0 mm exit pupilDetailed
Saturn150× · 300 mm 2.0 mm exit pupilDetailed
Jupiter150× · 300 mm 2.0 mm exit pupilDetailed
The Orion Nebula60× · 300 mm 5.0 mm exit pupilDetailed
The Andromeda Galaxy60× · 300 mm 5.0 mm exit pupilDetailed
The Hercules Cluster150× · 300 mm 2.0 mm exit pupilRecognisable
Photo credits

These thumbnails are built from real photographs, scaled and darkened by the same arithmetic as the large view.

  • The Moon: NASA Scientific Visualization Studio / LRO, public domain
  • The Orion Nebula: NASA, ESA, M. Robberto (heic0601a), CC BY 4.0
  • The Andromeda Galaxy: Adam Evans, Wikimedia Commons, CC BY 2.0
  • The Hercules Cluster: Wikimedia Commons, Messier_13.jpg, CC BY-SA

The numbers

GSO Dobson 300/1500Photo: Astroshop
Aperture300 mm
Focal ratio1500 mm · f/5.0
MountFull-size Dobsonian rocker box
Typical weight33 kg
Eyepieces25 mm
Useful magnification50× to 600× at 300 mm
Resolution (Dawes)0.4″ — the tightest double star this aperture can split
Faintest star, suburban skyaround magnitude 13.7
Observed price€899 seen 23 Oct 2026 at Astroshop

Made for

  • Nebulae, clusters and galaxies, by eye

    The reason people own these. Nothing else at the price shows as much.

  • The Moon and the planets

    Superb when the seeing allows, which is less often than the aperture would like.

  • The Sun

    In white light: sunspots with their penumbra, faculae near the edge, and granulation on a steady morning. Dawes' limit on the Sun: 0.4″ (116 ÷ 300 mm, arithmetic). It needs a certified cell over the front whose range holds its 356 mm outside diameter: the euro EMC SF100 (323–381 mm), €205 (seen 26 Sept 2026). Every time: certified filter over the front · finder capped · never an eyepiece filter · an adult with children · never without the filter · measure first.

Not made for

  • Learn my way around the sky

    Not the instrument to learn on. The field is narrow and the setup is a commitment.

  • Taking it with me

    No.

The Sun, safely

No solar filter in the box

The Sun with this model

It needs a certified cell over the front whose range holds its 356 mm outside diameter: the euro EMC SF100 (323–381 mm), €205 (seen 26 Sept 2026).

In white light: sunspots with their penumbra, faculae near the edge, and granulation on a steady morning. Dawes' limit on the Sun: 0.4″ (116 ÷ 300 mm, arithmetic).

Past about 100 to 125 mm, daytime air rather than aperture generally sets the limit on the Sun (experience: the AAVSO solar observing guide).

The listing gives a fit of 323–381 mm across the outside of the tube. Clear aperture 315 mm. The listing names no standard; no international standard exists for filters on telescopes, binoculars or lenses (AAS).

Where to buy

1 of these 1 links earn us a commission, marked above. Sorted by price, never by what pays. How this site is funded.

Every time

  • A certified solar filter over the FRONT of the instrument, fastened so it cannot slip or blow off.
  • Cap or remove the finder. It is a second telescope, and it has no filter.
  • Never a filter at the eyepiece end: the concentrated sunlight there can crack it in an instant.
  • With children, an adult is there every time.
  • Never look, or point, without the filter on. Check it before each use; a scratched or torn filter goes in the bin.
  • Measure before ordering. A cell that sits loose can fall off.
Sources for the Sun

The family it belongs to: 250–300 mm Dobsonian

What it does well

  • Spiral structure in the brighter galaxies, from a dark site
  • Enough light that a nebula filter finally has something to work with
  • Still the cheapest route to this much aperture by a wide margin

What it costs you

  • 40 kg in two or three pieces. It needs a car, a plan and a body that agrees
  • A cooling-down period of half an hour or more before it performs
  • Under a bright sky, most of this aperture is buying background glow

Worth knowing about this model

The plain 300 mm: a parabolic mirror, a Crayford focuser, a wooden rocker box, and nothing electronic. GSO makes the mirrors that several other brands sell under their own names. 1.5 m long and 19.5 kg of tube — it needs a car, a cupboard, and someone willing to carry it, every single night.

Everything about 250–300 mm Dobsonian →

Same family, other sizes

Compare it

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€899seen 23 Oct 2026 at Astroshop

Where to buy