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Buy the right telescope, not the biggest one

305×
Saturn at 305× in 305 mm — exit pupil 1.0 mm, Bortle 6 sky. Computed, not photographed.

250–300 mm Dobsonian

Bresser Messier 305/1525 Dobson

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

€1,265seen 7 Oct 2026 at Astroshop

See it at AstroshopAll the sellers
  • 305 mmAperture
  • f/5.0Focal ratio
  • 31 kgTypical weight
  • 51–610×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.
  • 31 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.

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 Moon61× · 305 mm 5.0 mm exit pupilDetailed
Saturn153× · 305 mm 2.0 mm exit pupilDetailed
Jupiter153× · 305 mm 2.0 mm exit pupilDetailed
The Orion Nebula61× · 305 mm 5.0 mm exit pupilDetailed
The Andromeda Galaxy61× · 305 mm 5.0 mm exit pupilDetailed
The Hercules Cluster153× · 305 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

Bresser Messier 305/1525 DobsonPhoto: Astroshop
Aperture305 mm
Focal ratio1525 mm · f/5.0
MountFull-size Dobsonian rocker box
Typical weight31 kg
Eyepieces25 mm
Useful magnification51× to 610× at 305 mm
Resolution (Dawes)0.4″ — the tightest double star this aperture can split
Faintest star, suburban skyaround magnitude 13.7
Observed price€1,265 seen 7 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 ÷ 305 mm, arithmetic). The maker's solar filter is in the box and made for this instrument: nothing to buy, nothing to measure. Every time: certified filter over the front · finder capped · never an eyepiece filter · an adult with children · never without the filter.

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

Solar filter in the box (read on the listing)

The Sun with this model

The maker's solar filter is in the box and made for this instrument: nothing to buy, nothing to measure.

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 ÷ 305 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).

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.
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

31 kg in all: the tube is 18.9 kg, the base 15 kg, per the spec table. With the tube pointed straight up, the eyepiece is 1.6 m off the ground. One eyepiece in the box: the 25 mm gives 61× on 305 mm, an exit pupil of 5 mm, and any higher power needs a second eyepiece bought separately. The finder is a 6×30.

Everything about 250–300 mm Dobsonian →

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Open this telescope in the simulatorIs it the right one for you? Ask the advisor

€1,265seen 7 Oct 2026 at Astroshop

Where to buy