Teleskops, Dobson, N 250/1250 DOB, GSO

A high-quality Dobsonian telescope with high-quality optics and a 250 mm 10 inch aperture. GSO Dobsonians feature the highest quality mirrors and impress due to their reasonable prices. This telescope is ideal for deep sky observation.

For many stargazers, deep sky observation starts off at an aperture of 10". As a matter of fact, many objects only start to reveal their true structures at this aperture. Despite this, the telescope is easily transportable and can even be placed on the back seat of a car.

The advantages at a glance:

• High-quality parabolic optics with 250mm aperture and 1250mm focal length.
• 94% reflection for a brighter, high-contrast image.
• Precise 2" Crayford focuser for precise focusing - with 1.25” reducer.
• Robust metal tube and adjustable mirror mount for optimal imaging, even after many years
• Easily upgradable, even for astrophotography
• Active primary mirror ventilation accelerates the telescope's temperature adaptation

GSO Dobsonian telescopes offer very good value for money - the optical performance of this reflecting telescope is outstanding, thanks to a high-quality primary mirror and improved mirror coating. The telescope also boasts very robust mechanics and ease of use. Dobsonian telescopes provide maximum astronomical performance within their price range.

Contrast and sharpness of the image - we recommend these telescopes to every amateur astronomer who wants to have fun observing. Due to better anti-reflective properties, nebulae and galaxies appear even brighter than in similar telescopes of the same aperture. The amount of detail observable on the Moon and planets is particularly good. The secondary mirror has been optimized and minimal obstruction; its thin spider vanes mean improved contrast and sharpness.

Setting up and getting started - GSO Dobsonians are simply and robustly designed, so even beginners will have no problem getting to grips with these telescopes. The instrument is ready for use within just a few minutes. Set down the rocker box - the lower part of the device - hang the tube with the round altitude bearings wheels into the receivers and tighten the springs. The instrument is then ready for observing.

Add-on options - GSO Dobsonians provide an ideal start in astronomy - you get a high-quality telescope. If then, later, you become interested in, for example, astrophotography, you can buy accessories that allow you to use the Newtonian on an equatorial mount. Also filters, additional eyepieces, corrector systems or even bino-viewers are available from us for this telescope.

The quality of the main mirror - the main mirror is the most important element involved in producing the image. We use selected GSO mirrors of the highest quality. Each mirror's performance is significantly better than diffraction-limited, guaranteeing you will enjoy your observing.

The Crayford focuser - a robust Crayford has some significant advantages over a simple rack and pinion focuser:

• smooth and sensitive adjustment for precise focusing even at high magnification
• gentle clamping of eyepieces and adapters via a clamping ring - so no screw pressing directly onto the eyepiece and possibly tilting it out of the optical axis.
• the use of ball-bearings means the image does not tilt during focusing - a problem with many cheap focusers.

Location and tracking of astronomical objects - the location and also the tracking of nebulae, galaxies and planets take place by hand with this telescope. For this reason, smooth and accurate movement is essential. A tension spring for elevation ensures controlled counter-pressure when slewing. So the telescope will not lose the object in view if, for example, the eyepiece is changed. The horizontal axis is also equipped with ball-bearings, ensuring smooth movement.

Active main mirror ventilation - telescopes are not always kept directly at the observing site. This can result in the primary mirror being at a different temperature to that of the environment. A fan, located behind the main mirror holder, blows the cooler air from outside onto the back of the main mirror, thus reducing the cooling time. Also, warm air from the OTA interior is removed faster.

It is not only important which telescope you buy, but also where you buy it.

We provide extra help:

• We are a leading telescope dealer and know these instruments like the back of our hands.
• We are always very happy to offer our assistance after your purchase, should you encounter any problems with your telescope’s setup or operation.
• Our ‘Telescope Basics’ booklet - an 80-page beginner's guide for our telescopes – is provided free of charge with every telescope we sell.

My tip: You can get this telescope for a lower price with the special radiant finder (Telrad), a Crayford focuser with gear reduction and an especially high-quality SWA eyepiece: Omegon Dobson telescope ProDob N 254/1250 Radiant.

The Rockerbox design has also been improved for the Omegon version.

(Stefan Taube)

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