The Image Acquisition System of the YNAO Multi-Function Astronomical Theodolite

A new telescope for astrometry, the YNAO Multi-Function Astronomical Theodolite, has been built in the Yunnan Observatory.Its main imaging device is a digital CCD camera without cooling.Two analog CCD cameras are used to measure telescope pointing errors in the azimuth and altitude directions, respectively.In using the telescope two sets of triggering signals are generated from the telescope control system, for controlling the digital camera and the analog-camera pair, respectively.The two image acquisition cards are separately installed in two workstations and can be operated in an external triggering mode.We describe the telescope operation mode which involves using rotation of the telescope.The observation mode can be described as two sets of exposures, which are before and after the telescope rotation, respectively.The start moments and amounts of exposures are set by external signals.The paper shows the block diagram of the entire image acquisition system and the flowchart of the software of using the system.The paper also gives the details of main programming methods of the software based on the VC++ and Sapera LT.As a demonstration of the effectiveness of the system, we provide a screenshot of the user interface of the software, some images acquired by the cameras, and an analysis of a stellar image recorded by the digital camera.