Guide · Updated 23 August 2026
130/900, 150/750 or a 150/1200 Dobsonian?
It is the most-asked question on the forums, and it gets the same answer every time, in forty replies. Here it is on one page: the three instruments show roughly the same thing, because they have roughly the same aperture. What separates them is what they stand on — and it is the mount, not the mirror, that decides whether you are still observing in March.
The short answer
- To observe, by eye, without complicating your life: the 150/1200 Dobsonian. The largest aperture, the steadiest mount, the fewest adjustments, and often the cheapest of the three. It is the forums' answer, and it is right.
- To observe with very little room: the 130 mm tabletop Newtonian (130/650), which is not in the title but beats the 130/900 on its EQ2 in every respect except maximum magnification, for €60 less.
- To start deep-sky photography one day: the 150/750 — but not on the light EQ3-2 of the kits. On a serious motorised mount (EQ5 or better), which is another budget, €900 and up. Otherwise it is a dearer, less stable Dobsonian.
- The 130/900 on an EQ2: the right optics on the wrong mount. If you are given one, keep it; do not buy one.
The detail product sheets never state: the 130/900 and the 150/750 have similar apertures — 130 mm against 150 mm, 33 % more light for the second — and the same observing discipline. What changes radically between the three is the stability of what sits under the tube.
What they actually show
The two circles below are computed: 130 mm on the left, 150 mm on the right, same eyepiece, same suburban sky. This is the optical difference between the 130/900 and the other two. It exists. It is small.
The 150/750 and the 150/1200 Dobsonian have exactly the same aperture, so they show the same thing. The 150/750 is shorter, hence 'faster' (f/5): a wider field for the same eyepiece, but coma at the edge and touchier collimation. The 150/1200 (f/8) is longer, more forgiving, more comfortable on planets, bulkier. At the eyepiece a beginner cannot tell them apart; in the cupboard they can.
The mount, which decides everything
The 130/900 in the kits comes on an EQ2: a light equatorial mount with axes to align on the pole, counterweights, and motions that go neither up-down nor left-right. It is the right mount for tracking an object for a long time, and that is precisely what a beginner does not do. What they do: point quickly, and need the image not to shake when they touch the focuser. The EQ2 fails both. On the forums the word that keeps coming back is 'wobbles'.
The 150/750 in the kits arrives on an EQ3-2: better, but still light for a 5 kg tube, and still equatorial — the same learning curve, counterweights included. It makes sense if you motorise it for photography, at which point you discover you needed an EQ5.
The Dobsonian is the same Newtonian tube on a box that turns. You push it; it stays. No counterweights, no alignment, no learning. It does not track the stars by itself — at high power you nudge the object back into the field every thirty seconds, and you get used to it in an evening. It is the mount that makes people observe.
Maximum useful magnification depends only on aperture: about 260× for 130 mm, 300× for 150 mm. The 130/900 is not 'more powerful' because it is longer; its focal length only changes which eyepiece gives which magnification.
Space, weight, storage
- 150/1200 Dobsonian: 1.2 m tube, 50 cm base, 18 kg in all, two trips to the garden. Stands in a corner; does not fit in a cupboard.
- 150/750 on EQ3-2: 70 cm tube, tripod and mount dismantled, 16 kg, three trips and ten minutes of setup.
- 130/900 on EQ2: 90 cm tube, 11 kg, the same ceremony, lighter.
- 130/650 tabletop Newtonian: 60 cm, 6 kg, one trip, a table. The only one of the four that fits in a cupboard.
The honest question: between deciding to go out and looking through the eyepiece, how many minutes will you accept? Beyond five, you go out less. The Dobsonian and the tabletop are at two minutes; the two equatorials at ten.
And photography?
It is the argument people buy the 150/750 for — 'later, I will do photography'. Three facts. One: deep-sky photography needs a stable motorised mount, and an EQ3-2 is not one; count €900 and up, tube included, for clean images. Two: the planets and the Moon photograph very well with a phone behind the eyepiece of a Dobsonian. Three: if the image is really what you want, a €450–750 smart telescope does it better, more simply, and with no mount to learn.
Buying a 150/750 on an EQ3-2 'for photography later' is buying a less stable, dearer Dobsonian for a future that will require another purchase anyway.
What next
If you were hesitating between these three, your budget is €250–400 and the answer is the 150/1200 Dobsonian — or the 130/650 tabletop if room is short. This site's advisor will say so with your sky and your home as inputs, and will also tell you what not to buy alongside.
Questions people ask
- 130/900 or 150/750: which is better to start?
- Neither, on the light equatorial mounts they are sold with. At similar aperture the 150/1200 Dobsonian is steadier, simpler and often cheaper. If room is short, a 130 mm tabletop Newtonian.
- Does the 130/900 magnify more than the 150/750?
- No. Maximum useful magnification depends on aperture, not focal length: about 260× for 130 mm, 300× for 150 mm. Focal length only changes which eyepiece gets you there.
- Can you do photography with a 150/750 on an EQ3-2?
- The Moon and planets, yes, with a phone or a small camera. Deep sky, no: it needs a stable motorised mount (EQ5 or better), which means a budget of €900 and up.
- Does a 150/1200 Dobsonian fit in a flat?
- Standing in a corner, yes: a 1.2 m tube on a 50 cm base. In a cupboard, no. On a balcony it is awkward and will not see what it was built for.
- 150/1200 or 200/1200 Dobsonian?
- The 200 mm shows noticeably more (78 % more light) for €80–150 more, but it weighs 25 kg and is as long. If you have the room and the back, the 200; if you hesitate, the 150 — the one you carry out is the one that shows.
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