This telescope is controlled by us before delivery and in any case pre-adjusted.

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GSD 400 TD - Truss Dobson 406mm aperture / 1800mm focal length - 16 "Truss Dobson

The largest Dobsonian from GSO - Truss Dobsonian - with excellent diffraction-limited optics



The advantages of the tubular construction:
A conventional Dobsonian in full tube design would no longer be useful to transport with this opening. That is why GSO has decided on an innovative space tube construction that combines quick assembly, easy transportability and adjustment stability. The grid "tubes" consist of shaped aluminum profiles, as known from tripods, which are light but stiff. We think the idea of ​​using tripod legs is very good, because the required properties (torsional rigidity with low weight) also apply to the tubular bars at Dobson's

Storage of the GSD 400 TD:

The azimuth bearing is an axial needle bearing whose rolling resistance is infinitely adjustable.

A completely new solution was found for the high-altitude camp:

This is a steel axis that carries the telescopic weight. The friction is set by a very precisely adjustable disc brake (see figure below) - on the one hand, the tube can stop in any position with changing eyepiece loads, on the other hand, smooth tracking is guaranteed without having to overcome a large breakaway torque (breakaway torque referred to in the mechanics the transition between static and sliding friction).

Setting the balance:

In addition, the position of the height axis can be set precisely: If e.g. permanently heavy accessories are mounted on the top of the tube, the center of gravity can simply be re-balanced.

The computer-optimized 18-point primary mirror cell:

The main mirror cell is the latest generation and computer-optimized. It guarantees an even support of the mirror and easy adjustment of the main mirror without tools.

The built-in fan accelerates the cooling of the BK7 main mirror.


2 "Crayford focuser with 1:10 micro reduction:

... a high-quality stored pull-out for precise focus rounds off the good overall impression. The pull-out has a ring clamp for 2 "and 1.25".

Technical specifications:


- 16 "(40.6 cm) primary mirror - diffraction limited

- Focal length: 1800mm, f / 4.5

- 2 "Crayford extension with reduction to 1.25" ring clamp
- 2 "35mm extension sleeve
- Easy access to the focus with cameras and all common eyepieces
- 18 point main mirror cell with ventilation
- Roller bearings in azimuth for easy adjustment

- Total weight including rocker box approx. 58 kg
- Weight of the rocker box approx. 25kg
- Diameter of the rocker box ... 82cm
- Height of the rocker box ... 70cm
- Weight of the tube approx. 33kg (can be dismantled into three individual parts)




Scope of delivery:

- 16 "truss tube Dobson with rocker box
- 8x50 viewfinder with multi-coated lens and quick coupling
- 2 "ERFLE 30 overview eyepiece with 67 ° field of view
- 1.25 "eyepiece Plössl 9mm
- Main mirror fan
- extensive German-language operating instructions
- Adjustment instructions



Construction and transport:

The GSD 400 TD can be disassembled into handy assemblies in just a few simple steps:


Upper tube connecting rods Rocker Box lower tube