Telescope SkyWatcher Skyliner 254/1200 Pyrex dobsonian

Price: 919.00 EUR / 3 173.12 Lt
899.00 EUR / 3 104.07 Lt.

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The optics of this Dobson has a diameter of 25cm (8`) and a focal length of 1200mm. Thus, the aperture ratio of 1:4.8 is reached. An optics like this provides a very strong light collecting ability (1275x). When the sky is rather dark, you can observe stars of marginal sizes of 14mag. Especially in case of apertures of 250mm, you can get best results for Deep Sky objects, which is not really possible with smaller telescopes. The secondary mirror rods are very thin and thus, the diffraction rate is very low. The optics` obstruction is about 25% because of the secondary mirror`s diameter (about 50 mm). The rocker box the telescope is mounted on is easy to handle. The telescope can thus be moved easily and with only a few fingers in azimuth and height The telescope can be moved with floating and pivot bearing.The optics stays stable in every position to allow a beautiful and undisturbed sky observation.Even if you want to magnify intensely, the observation will be pure fun. By the help of the 9x50mm finder scope with a fine reticule, it`s easy to find even faint objects. The new parabolic reflectors of this DOBSON-PX range are made of Pyrex. The Pyrex reflector bracket is not as vast as for example the common BK7 glass material. The dimension of BK7 is about 2x larger than with a Pyrex. This mirror can not easily be drafted. Thus, it remains in its geometric form even during the cooling time, and this is the difference to a reflector made of BK7 glass. Because of this, the mirror provides a better reproduction efficiency in the cooling down phase. Moreover, Pyrex can be parabolised much easier. However, this mirror doesn`t cool down in a shorter period of time than other mirror products.The mirrors are 75nm p.t.v. minimum or even better. Dobson Telescopes are equipped with a Strehl value of 0,8 or higher. This tells us about the optical efficiency and power of this telescope: If 80% of the light unite in the telescope`s diffraction slices, astronomers call this a diffraction limited optics. This means that the resolution of a telescope is only limited by the light`s diffraction. As this chiffre can not be 100%, the definition of the diffraction limit has been fixed on 0,8. Thus, you have a recommendable optics. This telescope has a Pyrex mirror. This type of glass exhibits much smaller thermal expansion than, for example, the commonly used BK7 glass - which is about 2X more than Pyrex. During the cooling phase, the mirror does not warp very much and so keeps its geometric shape much better than a BK7 mirror. So, as a result, the mirror offers better image quality during the cooling phase. Also, Pyrex is easier to figure into a parabola. However, it does not cool down any faster than other mirror materials. The mirror meets at least 75nm p.t.v. or better. So the well-known precision condition Lambda/8 is more than satisfied. The telescopes have 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. 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. Technical characteristics: Objective Diameter: 254 mm Telescope Focal Length: 1200 mm Highest Practical Power (Potential): x300 Focal Length/Diameter Realtion F: 8 Wooden Alt-Azimuth Mount