Celestron CG-5 Computerized German Equatorial Mount 91518 GPS-compatible with optional CN16 GPS Accessory (#93963) Proven NexStar computer control technology RS-232 communication port on hand control to control the telescope via a personal compute Autoguider port for long exposure astrophotography 40,000+ object database with 400 user-definable objects and expanded informationon over 200 objects