Main instrument

Newtonian reflector

The main instrument is a Newtonian reflector with a nominal aperture of 600 mm, a focal length of 2,991 mm and a focal ratio of f/5. The instrument is permanently mounted and designed to combine substantial light-gathering capability with high mechanical stability.

At a glance

Optical design: Newtonian reflector
Nominal aperture: 600 mm
Focal length: 2,991 mm
Focal ratio: f/5
Secondary mirror: 140 mm
Linear central obstruction: Approximately 23%
Primary mirror cell: 36-point axial support
Radial mirror support: 6 whiffletree arms, 12 contact points
Spider: AstroSystems Super Duty II, Style 5
Secondary holder: AstroSystems 5.5 inch
Focuser: Starlight Instruments Feather Touch FTF3545B-A
Focuser diameter: 3.5 inches
Focuser travel: 114 mm
Theoretical resolution: Approximately 0.19 arcseconds
Visual limiting magnitude: Approximately 16.4 mag
Finder: 8×50

Construction

Tube structure

The Newtonian reflector is built around an approximately three metre long aluminium tube. To combine effective optical baffling with high mechanical stability, the tube contains eight individually fitted internal baffles. The baffles reduce stray light while also acting as structural reinforcements, increasing resistance to flexure as the telescope is pointed to different parts of the sky.

The tube is carried by substantial tube rings and a long mounting rail that distributes the load to the mount. The structure is supplemented by support trusses made from solid 16 mm aluminium rod. The refractor is mounted in parallel on a separate rail integrated into the tube-ring system.

Primary optics

Primary mirror support

The primary mirror rests axially on a 36-point mirror cell, distributing its weight across a large number of support points.

Radial edge support is provided by six articulated whiffletree arms, each carrying two nylon bearings in contact with the mirror edge. The twelve contact points distribute lateral loads around the mirror as the telescope changes orientation.

Secondary system

The 140 mm secondary mirror is mounted in an AstroSystems Super Duty II Spider, Style 5, with a separate AstroSystems secondary holder for a 5.5-inch mirror. The assembly is dimensioned for large secondary mirrors and provides a stable support with accurate collimation adjustment.

Focus

Focusing

The Newtonian reflector uses a 3.5-inch Starlight Instruments Feather Touch FTF3545B-A. The focuser has a rack-and-pinion mechanism, 10:1 fine reduction, brake and 114 mm of travel. Its mechanically robust design supports both larger optical accessories and camera equipment.

Image recording

Nikon D6

A Nikon D6 is used for the photographic documentation of visual observations. The camera has a 35.9 × 23.9 mm FX CMOS sensor with 20.8 million effective pixels. Documentation images are normally captured as single short exposures and subsequently processed to approximate the object's visual appearance at the eyepiece.

Use: Documentation of visual observations
Sensor type: FX CMOS
Sensor size: 35.9 × 23.9 mm
Effective pixels: 20.8 million
Maximum image size: 5,568 × 3,712 pixels
Image data: NEF (RAW), 12 or 14 bit

Astronomical camera

SBIG STXL-11002M

For astronomical CCD imaging, the observatory also has an SBIG STXL-11002M. The camera uses a monochrome KAI-11002 sensor and is equipped with thermoelectric cooling and 16-bit A/D conversion.

The camera system has an eight-position filter wheel for 50 mm round filters. Seven filters are installed: luminance (L), red (R), green (G), blue (B), Hα, OIII and SII.

Sensor: KAI-11002, monochrome CCD
Resolution: 4,008 × 2,672 pixels
Pixel size: 9 µm
Sensor size: 37.3 × 25.7 mm
A/D conversion: 16 bit
Filter wheel: 8 positions, 50 mm filters
Installed filters: L, R, G, B, Hα, OIII, SII
Cooling: Thermoelectric

Operating environment

Thermal stabilization and humidity protection

The primary mirror has active temperature equalization using a fan directed at the back of the mirror. The system is used to accelerate thermal adaptation between the mirror and ambient air before observing.

When the telescope is not in use, relative humidity inside the telescope is monitored continuously. An automatically controlled heating element is activated when humidity exceeds 70% and remains active until it has fallen to 60%. The difference between the switch-on and switch-off thresholds reduces the risk of condensation and moisture exposure on optics and mechanical components without requiring continuous heating.