I've used this site lots of times. It's fun to see where the ships are. Sometimes when they are crusing through no man's land there's no data, so you can't find them. If anyone's interested, here are the call signs for all three of Regent's ships - you can enter the call sign and the system will find the ship if data is available.
Mariner - C6VV8
Navigator - ZCDT7
Voyager - C6SW3