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





The mechanical concept of the „Infinity NL“ series simply is:

- Low weight and packing volume
- Easy and robust handling
- Tool-free setup within 10 minutes
- Smooth manual guidance
- High stability, vibration- resistant design
- Two well thought-out transport modes

All these topics were consequently realized during the development and construction phases. They have also been tested under real-life conditions for many years during countless clear nights under the sky and have been continously improved on that basis.

Low weight construction? Yes! Extreme and super delicate construction? No. Some of the components and assemblies were deliberately kept a bit more robust to achieve the high stability of these telescopes. Concerning the handling many goals were kept in mind: a setup containing only a few steps, that are easy to implement without using any tools; dimensions of knurled screws that allow for a good grip even under coldest winter conditions; an adjustment routine for the main mirror that can be carried out from the top of the mirror box; easy removal of the main mirror from the construction for cleaning purposes ... and many more details that in combination will define your experiences with your Infinity NL out there under the stars.

Looking for a well-thought-out telescope concept that has been proven time and again under the night-sky, realizing secret wishes of the active astronomer? You´ve found it in the „Infinity NL“ series by Spacewalk Telescopes.

1) Secondary Cage


The secondary cage´s two ring components are made of a light-weight aluminum square tube and completed with a matt black powder coating. They are connected via four weight-optimized wooden squares.

The stable spider keeps the secondary mirror firmly in the intended position. It is made of an only 0.5mm thin brass-sheet therefore keeping the creation of spikes to a minimum. The secondary mirror is attached to a rigid holder made from black POM and can be adjusted via three adjustment- and counter screws. A heating unit prevents the mirror from fogging up during humid nights.

The precise 2“ focuser made by the company „Moonlite“ offers an 1:8 reduction ratio and realizes an especially smooth and exact focussing process. Depending on the telescope size an optical 6x30 or 8/50 finder is found next to the focuser. However the telescope is also prepared for the alternative installation of a Telrad finder. Optionally a filter slider by the company „Spheretec“ including up to three filters can also be integrated.

The secondary baffle has been optimized for function during windier conditions and is made of durable matt black plastic. It is firmly attached to the telescope via four star knob nuts.

2) Trusses and Struts


The secondary cage and the mirror box are connected via eight anodized aluminum trusses. The upper truss holders combine two trusses respectively to a permanent pair.

The lower truss holders are permanently attached to the side bearings and the mirror box. During the telescope setup process every one of the described truss pairs is attached to the these via star knob nuts. The upper truss holders contain a groove fitting to an easy and robust clamping mechanism located at the lower ring of the secondary cage.

Between the side bearings one cross brace and two diagonal braces guarantee maximal stability. This contributes to a direct and precise telescope guidance that in turn leads to maximal comfort during observing.

3) Mirrorcell and Mirrorbox


The mirrorbox is made of extremely solid multi-bonded birch multiplex wood. Its side panels are glued and bolted together as well as strengthened with six reinforcement units located at the corners. All of these measures lead to a very rigid construction with exceptional stability.

Since the highly precise primary mirror is manufactured in-house from an only 25mm (16“ telescope) or 31mm (20“ telescope) blank, it is exceptionally thin. Therefore a simple standard mirror cell does not offer enough support to guarantee maximum performance. Instead the basis of the Spacewalk Telescopes mirror cells is created by highly stable aluminum profiles. The primary itself rests on a 18-point based, floating support construction and is also laterally supported by ball bearings located exactly at the line representig the mirror´s center of gravity.

Within the telescope the cells adjustment can be done via two larger, easy-to-grip star knob nuts from above the cell. That way the adjustment process is very comfortable and can be finished very quickly.

In case the primary mirror needs to be removed from the telescope - for example for cleaning purposes or to keep it safe when taking it along on a vacation – the „Infinity NL“ Series offers an easy way of access: After loosening four knurled nuts the panel above the primary mirror can be removed providing direct access.

Furthermore during the telescope setup and dismantling processes a cover plate for the mirror box is put in place, which protects the primary from eventually dropped screws or similar accidents. A cooling fan integrated into the plate can be used to quickly cool the primary down to ambient temperature after the setup. This plate additionally functions as protection and dust cover when the telescope is not in use.

4) Rockerbox


The two side panels of the rockerbox form the counterpart for the tread areas of the side bearings. The sliding mechanism between these components as well as the one between the ground plate below the box and the box bottom is realized via the proven material combination of teflon and ebony, ensuring smooth and exact guidance of the telescope in both axes. To reduce weight of the box, the side panels of the 20“ telescope contain a pattern of machined holes.

The floor of the rockerbox includes an opening with an aluminum plate inside, preparing every telescope for the optional integration of digital setting circles (BDSC).