Dobsonian telescopes are among the most practical instruments in astronomy. They are of simple construction and yet a brilliant idea. They essentially consist of two parts: firstly the optics, which in most cases is a solid tube or truss tube design; and secondly the mount, a wooden box (also called a 'rocker box') which sits on the ground and into which the telescope is inserted. This design allows you to begin observing sessions immediately without first having to spend time setting up and aligning a complicated mount. The basic idea of the Dobsonian design came from the wish to have a big telescope at a low price, a wish that has succeeded brilliantly. A true fan base has developed since the invention of the Dobsonian telescope which is dedicated to these instruments and their fascinating simplicity and to the idea of 'high performance at low price'.
The DOBSON telescopes from the house of SKYWATCHER convince by technical innovation and functional Design.
A simple, elegant form of an alt-azimuth mount made to carry a Newtonian reflector was popularized by John Dobson in the late 1970's. In its simplest form, the Dobsonian mount consists of a box which allows the optical tube assembly to pivot in altitude, while the box itself is swivelled on a base in azimuth. Normally such mounts are moved by hand rather than motor driven. Their main advantages are low cost, fast easy setup and ability to make a mount big enough for larger tubes.
The devices have handles, which are very useful both to transport and for adjustment the elevator axle.
The telescope has a 2"-Focuser with adapter for 1,25"[ - ] like that is also a later ascent to 2"-Apex eyepieces without problems possible.
Precision figured surfaces: the mirror of this telescope is made of BK7 glass and meets 75nm ptv or better, so the well-known precision condition Lambda/8 is more than satisfied. The telescope has a Strehl ratio of 0.8 or higher. This value expresses something of the optical performance and therefore the quality of the figured surfaces. When theoretically 80% of the light is incorporated in the Airy disk of the telescope image, the optics are described as 'diffraction limited'. That means that the resolution of a telescope is only limited by the diffraction of light. As it is not possible for this to be 100%, the definition of the diffraction limit has been set at 0.8. This always means that you have excellent optics (other systemic losses are not included here).
The 2" focuser is smooth and comes provided with a 1.25" reducer. The finder scope has a fine crosshair, allowing easy location of even the somewhat fainter objects.
The Skywatcher rocker box is very easy to use. The telescope can be pointed in azimuth and altitude easily and smoothly by using only a couple of fingers. The telescope moves on slide and pivot bearings. It remains stable in any position, allowing highly enjoyable observing. And observing still remains a joy even at higher magnifications. The Tension Control System also lets you easily adjust the friction setting and so the amount of resistance when moving the optics on the rocker box. This allows you to always have the appropriate resistance set.
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Dobsonian telescopes offer a lot of telescope for the money. They are often purchased by beginners due to their simplicity and ease of use. Tracking is done manually. These instruments are primarily designed for visual observing. Their relatively large apertures mean you can resolve globular clusters and also see some structure in nebulae. Photography of the Moon and Sun are also possible with the appropriate accessories. Photography of other celestial objects requires a mount with tracking capabilities. This mount can be retrofitted later.