Astrophotography by Torsten Mueller


Over the years, the optical and mechanical equipment was steadily improved (in terms of weight, diameter, size and $$$). But now and for this observatory, the setup seems quite completed.

The goal for the actual setup was:
There are very different objects in the sky, and each of them may require a dedicated setup. I´d like to photograph only - no visual observing, and then mostly faint and small galaxies. The system, which is described here, was choosen especially for this purpose.

The foundation of the system is a Skywatcher EQ-8 german equatorial mount on a heavy weight steel tripod. This mount is controlled over a USB Interface directly (without hand controller) by the PC.

The optical assembly is a 12" Ritchey Chretien type carbon truss telescope. This telescope provide a 12 inch (305mm) mirror with 2600mm focal length. That gives a focal ratio of f/8. This ratio is quite "slow" for most targets and gives a very narrow field of view. To be more flexible, most of the time, a 0.67 (TS optics CCD67) focal reducer in installed in the optical path. The resulting focal length of 1630 mm is still appropriate for many of my favourite targets.

As main camera i´m using a ZWO ASI 1600 cooled monochrome camera. This camera provides 3.8um pixel, and 16 megapixel overall. With the 12" RC, this will always result in so called oversampling. But the camera is super versatile, i can use it binned , with ~8um pixels or with a small APO to get a real wide field of view, or using a Barlow lens to do some planetary imaging.

The mount needs to be guided (corrected for worm drive and polar aligment errors) , that is done by a Starlight XPress Lodestar camera mounted in an off axis guider (TS OAG 27).
When the system is remote controlled, a motor driven focuser is vital. Therefore, i adopted the open source project "myFocuserPro2", but with the most simple approach. No buttons, no display, just the motor control and ASCOM interface. Most of the time i´m doing luminance shots, that means black/white images.

But if a target is good for color photography, a filter wheel is also always in front of the camera. For remote control, its quite good to have all the reasonable filters in place. I build a motor and logic control around a 12 position Moravian filter wheel (The Moravian wheels are controlled directly by the Moravian camera, so they are not usable standalone or with a different camera brand). This electronic consists of an Arduino nano and a small scale microstepping driver (thanks to the 3D printer community, they brought these little controllers to the public). Of course, a proper ASCOM driver was also developed, to be able to integrate it seamless into the imaging workflow.
With space for 12 filtes,nearly every use case is possible. At the moment, the following filters are installed and usable: