GSO Dobsonian GSD 250 C review

BBC Sky at Night Magazine reviews the GSO Dobsonian GSD 250 C Telescope

Our rating 
4.5 out of 5 star rating 4.5
£436
Price correct at time of review
GSO Dobsonian GSD 250 C

Price: £436.00
Aperture: 10 inches (250mm)
Focal Length: 1,250mm; f/5
Eyepieces: 32mm RK, 2-inch fit
Finderscope: 8×50 straight-through
Weight: 27.7kg
Supplier: Teleskop-Service
Telephone: 49 089 189 2870
Website: www.teleskop-express.de

The GSO is a steel-tubed telescope with a large, sturdy base and an appealing price tag.

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The telescope tube does not come to pieces or collapse down like the others, so it comes in a pretty large box.

Constructing the base is straightforward, especially if you have ever built flat-pack furniture.

A small Allen key is provided along with a tiny diagram, so good eyesight plus a screwdriver and 13mm spanner are all that’s required to put it together.

The mirror is held in a substantial three-point cell and is well protected from damage and stray light inside the rigid tube.

This meant the GSO was well collimated after its journey to us. Adjusting the secondary mirror requires a screwdriver, and although we didn’t like having to hold tools above the primary mirror, collimation was easy to achieve.

To aid mirror cooling, a battery-powered fan is thoughtfully provided.

The shiny silver tube is a little tricky to grasp and we felt that a simple handle would be a thoughtful addition.

The mount turns smoothly, thanks to a large roller bearing in the base section and Teflon pads, which support the plastic altitude bearings on either side of the tube.

In use, these worked beautifully, with just the right amount of friction generated by the downwards force from two springs that also keep the scope safely secured.

The tube seemed well balanced even when we tried heavier eyepieces than the supplied 32mm wide-field model.

The scope could also be re-mounted onto an equatorial mount if you have suitable tube rings.

Like many scopes of this ilk, the GSO comes with an eyepiece and accessory tray.

The 2-inch Crayford focuser is very solidly built, with tension and locking screws that functioned very effectively.

Brass compression rings are provided in the focuser and the 1.25-inch adaptor to protect your eyepieces.

There’s a straight-through 8×50 finderscope held in a spring-loaded holder, which we found easy to adjust.

The views through this kind of finderscope are the same way up as the main scope, which you may find convenient.

Beehive beauty

Our first view through the 32mm eyepiece was of the Beehive Cluster and we were impressed with the crisp stars and delightful variations of colour.

The edge of the field beyond about 70 per cent was less sharp with some signs of coma (distortion of the star shapes), but this did not detract from what was a very enjoyable experience.

We turned towards nearby Mars, which exhibited good colour, but we needed to use shorter focal length eyepieces to magnify it to a reasonable size.

This tube provided the best shielding from stray light and the contrast was good enough to pick out the spiral structure of the Whirlpool Galaxy (M51) in a fairly light polluted area.

Although at times we felt the azimuth bearing was a bit too easy to turn – we knocked the scope off target when changing eyepieces – for simplicity and reliability, this scope ticks all the right boxes.

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A version of this article appeared in the June 2010 issue of Sky at Night Magazine