20"f/3 and 25"f/3 Dobsonian Telescopes: Summary Description

The 25 inch "Horizon" Dobsonian is "Spacewalk Telescope´s" high-end flag-ship model. The related „Horizon“ telescope series includes the large 25“ version as well as a 20“ model, both with the key characteristic of an extremely short focal ratio of f/3.2. This allows for a comfortable, very low viewing height, which comes to only 150cm for the 20“ dobsonian and 180cm for the 25“ model, therefore setting new standards on the telescope market.

The only 31mm(20“ version) or 35mm(25“ version) thin main mirrors are completely made in Germany, from the blank disk to the final parabolic form. They are carefully ground, polished and measured within the Spacewalk Telescopes manufacturing facilities and come to you with an interferometric test certificate.

Being very thin, a primary made by "Spacewalk Telescopes" is lightweight and additionally cools down very fast. The secondary mirrors are made by a renowned manufacturer in the USA and have a surface accuracy of better than lambda/10. Both of these high-quality optics form a very efficient optical system offering sharp, high-contrast images event when using highest magnifications.

The telescope mechanics have been constructed in a lightweight design and are optimized for the exepctionally short focal ratio with an emphasis on quality materials like carbon fiber components and welded, matt-black powder-coated aluminum frames and components. The truss holders and mirror cell components are milled from solid material to guarantee optimal performance. Additionally every Horizon telescope is prepared for the optional integration of Digital Setting Circles (BDSC), that offer the wireless bluetooth communication with your smartphone or tablet, tracing the telescope´s current position within an interactive star chart on your screen.

With a "Horizon" dobsonian built by "Spacewalk Telescopes" you get to explore the distant corners of the universe using a revolutionary design: a high- quality optical system with exceptional short focal length, embedded within a sophisticated mechanical construction, all tested and proven time and again during countless nights under the stars.

1) Short Profile

Available: 500/1600mm and 635/2000mm

Ultra-thin Primary (31/35mm Thickness)
Strehl Ratio of Primary > 0.90 / 0.85
Secondary made in the USA (lambda/10)
Including interferometrical test certificates
Short cool down periods

Primary can be aligned from the top

Welded frames with black powder-coating
Trusses made from carbon fiber
Low weight and small packing volume
High stability, vibration- resistant design

Setup within 10-15 minutes
Three transport modes

2" focuser with an 1:11 reduction ratio
Optional filter slider made by Spheretec
Optional Digital Setting Circles

2) Detailed Description of the "Horizon" Telescope Series

The following pages contain not only all relevant information about the telescopes, their optical components and mechanical concept, but also details on transport modes and of course the most important technical data has also been summarized for you:

3) Star Observing with the "Horizon" Telescope Series

How does a f/3.2 Dobsonian Telescope behave under starry nights? Are there any impacts on the image quality? Do you need a Coma Corrector and what sort of eyepieces a suitable for a telescope with such an extraordinary short focal ratio?

4) Information for offline use

The following links lead to a detailed document containing all important information on the Infinity NL telescope series as well as to the current price list, both intended for downloading and/or printing:

5) The universe as seen through a 20" dobsonian telescope

Sketches are the best way to accurately represent the way in which an astronomical object appears when seen through the eyepiece of a telescope. Share the experiences of seeing the universe through a 20" telescope under a dark sky with your own eyes and discover star clusters, gaseous nebulae and galaxies drawn by an experienced fellow astronomer.

(Only available in german!)