20"f/3 and 25"f/3 Dobsonian Telescopes: Concept




The „Horizon“-Series - Setting new Standards


Astronomy and especially observing our universe first hand means broadening your horizon. It is about walking new paths and delving ever deeper into the universe, it is about discovering new objects located many billions of lightyears from our own planet that may have been hidden from us before and so much more.

The „Horizon“- series paves the way to let you walk these paths, revealing the universe in unknown brightness, sharpness of detail and color ranges to you.

Large amounts of light are needed to visit all these wonders, so in developing the new series Spacewalk Telescopes has now made an even larger aperture available to you, the flag-ship model - Horizon 25“.

While still coming with a lightweight construction this 25 inches f/3.2 dobsonian telescope includes a primary mirror with 635mm diameter, capable of collecting more than 11000 times the light that the naked eye alone provides, unvealing many of the secrets of in the vastness of space. In a dark clear night, stars of the 17th magnitude and even fainter ones can be observed, providing access to special objects like fine singular stars within the Andromeda galaxy. With your "Horizon" Telescope efficiently capturing countless photons for you even quasars at the very edge of the observable universe are within your reach, huge black holes shining a trillion times brighter than our own sun.

But then large apertures usually mean longer focal lengths, inevitably leading to the well-known challenges of elevated viewing heights. To counteract this fact, the chosen focal ratio for the Horizon series is extremely short, meaning a ratio of f/3.2 . A Horizon telescope offers the best of both worlds, a large primary mirror and a nevertheless comfortable viewing height. With a 20“ Horizon and its 150cm eyepiece height at the zenith your feet can still be placed firmly on the ground at all times and for the 180cm of the 25“ model a small pedestal is more than enough to reach the eyepiece.

The complete telescope design was adapted to the unusual focal ratio, so the Horizon series by Spacewalk Telescopes is an entirely new development from the ground up. High-quality materials like light carbon fiber trusses, welded and matt-black powder-coated aluminum frames and components milled from solid material are the basis for these high-end telescopes. This leads not only to an extremely stable construction but also a special design with clear lines, forming a plain and practical, yet revolutionary concept.

The most essential part of every telescope are the optical components. This is why the thin high-quality primary mirrors, from the blank disk to the final parabolic form, are completely made here in the south-west of Germany. They are carefully ground, polished and measured within the Spacewalk Telescopes manufacturing facilities, undergoing many interferometrical tests during the process to ensure top quality. The secondary mirrors are sourced from a renowned manufacturer in the USA and have a surface accuracy of better than lambda/10. Both mirrors come with interferometrical test certificates and combined they create sharp and crystal clear images.

The realization of a concept containing such an extremely short focal length was only made possible by significant advancements concerning the design of matching eyepieces during recent years.

Innovative companies like „TeleVue“ have especially contributed to these improvements. Not only does „TeleVue“ offer high-end eyepiece series like the well-known „Nagler“ or „Ethos“ pieces but with the „TeleVue ParaCorr“ there is also a coma corrector available. Combined with the described eye pieces the ParaCorr easily handles the focal ratio of f/3.2 used within the Spacewalk Telescopes „Horizon“ series. Even at the edge of the viewing field stars still appear as almost perfectly sharp point images.

For more than two years the Horizon series including all described components has been thoroughly and successfully tested during countless clear nights under the stars, proving the functionality and the endless opportunities.

Let the Horizon dobsonian telescopes widely open the window to a new universe to you and you will be amazed by the bright view. Unusual objects, finest details, endless possibilities, this is what these high-quality and innovative instruments were meant to do.