16"+20" Dobsonian Telescope "Infinity NL": Optics





Silver-white shining clouds on the mountainsides of Martian vulcanos, finest details in colorful planetary nebulae, singular stars within the densly packed centers of globular clusters or the slim jet of the Messier 87 black hole - to observe these things successfully not only a large telescope aperture is needed but high quality optics are also essential.

This is why the core of all „Infinity NL“ telescopes is an optical system of very high quality which not only refers to the primary but also the secondary mirror. This combination will fascinate you with sharp high contrast images and show you countless wonderful details that will surprise you time and again.


1) The Primary Mirror


Every primary mirror within an „Infinity NL“ telescope is made in Germany within the facilities of Spacewalk Telescopes. The high quality blank disk made by "Schott" is carefully ground, polished and given its parabolic form there, creating a precise and unique mirror for your telescope.

During the whole manufacturing process the optical quality of the mirror is constantly monitored. This includes inspections of the surface quality during grinding and polishing processes as well as several interfeometrical analyses of the parabola when giving the mirror the desired parabolic shape. Especially the final measurement is of great importance since this is where the information about the quality of the finished product is determined. This is why a lot of effort is put into the measurement, averaging many interferograms to define the Strehl-ratio and therefore the performance capability of the mirror as precisely as possible.

You will receive an intererometric test protocol including all information an a specific description of your unique mirror in print.

The primary mirror is declared finished when the Strehl-ratio measured by "Spacewalk Telescopes" is at least S=0.90 .

Another important and often neglected aspect of a primary mirror is its edge thickness. The Spacewalk Telescope primaries have an edge thickness of 25mm or 31mm depending on the aperture and therefore qualify as very thin. As a result they cool down incredibly fast, giving you the opportunity to use even high magnifications already after a very short time.

After all why waisting precious observing time?


2) The Secondary Mirror


Concerning the optical performance of a telescope not only the primary but of course also the secondary has to be considered. This fact is often being neglected but nevertheless critical.

The secondary mirrors integrated into Spacewalk Telescopes' instruments are sourced from a renowned manufacturer in the USA and have a surface accuracy of better than lambda/10. Optionally an even better quality is available at an extra charge

Every secondary mirror also comes with a test protocol informing you exactly about its optical performance.