How to build a serial cable for Celestron NexStar telescopes.

[-] We need a female Sub-D 9pin serial connector. This piece will fit inside your computer's serial port and/or usb adapter.

[-] To be sure our cable will work smoothly with any program, we should short some pins on the serial port to create "fake" handshake signals. Otherwise, we could have problems to talk with a "three pin only" serial device. In the following schematics we can see the serial port pinout: we're going to short together RTS/CTS (pins 7 and 8) and DTR/DSR (pins 4 and 6). We will then connect the cable in the following way: wire A to pin 3 (TX); wire C to pin 5 (GND); and wire D to pin 2 (RX).

[-] This is the back of the serial connector with two little wires we will use to make the shorts:

[-] Once the wires have been soldered the connector will look like this:

[-] We proceed to solder the wires to the connector:

[-] We can finally close the Sub-D box. Note the metallic "stop" at the bottom of the box that prevents the wires to be pulled too much.

[-] The cable is finished!