Second hand Celestron 10m PC cable. This is a serial type cable so one end will go into your handset and the other will go into a serial port. Please note most modern computers or laptops don't have a serial port, so you may need to buy a serial to USB adaptor.
Second hand USB to serial adaptor in excellent condition. Comes complete with drivers on a mini CD. Ideal for updating firmware on older Skywatcher and Celestron mounts that come with the serial PC cable.