An Image Processing System for a Multi-Function Astronomical Theodolite

A new Multi-Function Astronomical Theodolite has been built in the Yunnan Observatory.Its main imaging device is a digital CCD camera without cooling.This paper presents an image processing system for the Multi-Function Astronomical Theodolite.The system is used to determine the centers of the stellar profiles in images obtained by the theodolite.The algorithm of the image-processing system includes two main parts, for searching the star and centering the star (object-centering), respectively.An image obtained with this instrument is unusual as it includes only one star.This makes it possible to adopt an efficient searching algorithm for the system.This is to smooth the image with a suitable method, then find the maximum-value pixel as the initial location of the center of the star.After comparing commonly used centering methods in astrometry for the adaptability, accuracy, calculation amount, and programming difficulty, we decide to use the method of two-dimensional modified moments as the object-centering method.The paper shows a block diagram of the image processing system and a program flowchart of the corresponding software written in the VC++.The paper also shows the main design of the program, a screenshot of the user interface of the software, and results of using the object-centering method to a star, an artificial stellar profile, and an aperture profile (which is through the axis collimator on the instrument).The paper finally presents a brief analysis of these results.