BMK10k: an autonomous robotic observatory with fail-safe industrial components

The BMK10k is a 30cm-aperture lens telescope ‘Ballistische Messkammer 75/2,5/18’, now equipped with a 100Megapixel STA1600LN CCD camera. With a plate scale of 2.54 arcsec per pixel, it delivers an astrometrically well-corrected field of view of 7.25° × 7.25°. We have roboticized it with the intention of operating it from Cerro Armazones, Chile, where it saw first light in August 2019. It is currently in commissioning. Among other applications, we plan to use it to observe the Southern PLATO Field (SPF) almost continuously for three years in preparation for the PLATO satellite, which will have much reduced spatial resolution in comparison. The telescope mount was retrofitted with modern servo motors and an industrial Beckhoff programmable logic controller (PLC), allowing reliable remote telescope control, environmental monitoring, dome control, with a separate PLC ensuring safely measures to protect the telescope in case of communication loss or power failure. Communications between the TCS and the PLC firmware are accomplished with Beckhoff TwinCAT Automation Device Specification (ADS) over TCP/IP. Real-time response is realised within the PLC, and ADS has latency times on the order of a few 100 ms, sufficient for high-level control of the telescope. Using off-the-shelf industrial components has proven to be a cost-effective and reliable method of operating a fully autonomous observatory.