There are a number of ways to hook up a GPS you already own to one of Celestron’s current generation of NexStar telescopes.
The first way is via your computer and the serial cable supplied with many hiking-navigation GPS units. With the cable, connect your GPS to your computer. The GPS should also be configured to run in NMEA (National Marine Electronics Association) mode. This sets the GPS into a standard mode that will allow it to communicate properly with NexGPS. Running the NexGPS program (bundled with Celestron’s NexRemote telescope control software), the location and time information can be fed to your mount via the hand control for use in aligning your scope.
Another more direct way is to use the AUX port on your scope mount (or the AUX port accessory for the Advanced GT mount) and an adapter cable for your particular brand of GPS to get the time-site data. These adapters are available from Earthshine Technologies and are used with the serial adapter that came with your GPS (or is available through your GPS manufacturer):