if u have a digital camera , keep the led 'on' in a dark room , focus the camera , shutter time max (say 10sec) .
and in the photo u can see the IR led glowing brightly (some use ir filter , my olympus worked well)
You can put and IR receiver/detector on the scope and see if you see a signal on the scope when it nears it. I freind that had a TV shop had a cheap card that would light up if you point a remove at it. To test remotes.
I would google for that. Or camera/video recorder in a dark room like akg mentioned. You have a cell phone with a camera?