Star mappers are used for high accuracy attitude determination of spacecrafts. The light collecting optical system is either a catadioptric lens or a refractive lens. The catadioptric lens has the advantage of wider spectral coverage. For this type of application a constant and symmetric blur diameter over the entire field of view of the lens is required. A compact catadioptric lens was designed which covers a total field of 8 degrees. The design was compact, easy-to-align and does not involve any aspheric surfaces. The constancy of blur diameter with FOV was very good at +10 micron defocus plane.