corryhully wrote:
as mentioned a hoya 720 is the way, but first check whether your camera is fitted with a hot mirror. if it is. no go.
to check, turn off the lights in a darkened room and point a tv remote control at the lens. if the light from the remote shows up you are good to go.
If you're using a DSLR, you will either to be viewing in 'Live View' mode or snapping an exposure of the remote while pressing one of the remote's buttons.