We present an X-Ray telescope prepared for VZLUSAT-1, the first Czech CubeSat.
The telescope utilizes the Timepix detector, a compact pixel detector sensitive
to hard X-ray radiation. It is suitable for detecting extraterrestrial X-Rays
due to its low noise characteristics, which enables measuring without special
cooling. A modified USB interface (developed by IEAP at CTU in Prague) is used
for low-level control of the Timepix. An additional 8-bit Atmel microcontroller
is dedicated to command the detector and to process the data onboard the
satellite. We present software methods for onboard post-processing of captured
images, which are suitable for implementation under the constraints of the
low-powered embedded hardware. Several measuring modes are prepared for
different scenarios including single picture exposure; solar UV-light triggered
exposure, and long-term all-sky monitoring. VZLUSAT-1 was successfully launched
on June 26th, 2017.