If you are trying to go with current methodology you can take pictures of refracted light and call it a ghost. Really you do not need any of that. "ghosts" never just sit around doing nothing. Find the purpose in real hauntings, unlock that mystery and you will never fail to see or feel them if that is what God desires. Forgive me for I disagreeumptions, but if you are called to be a ghost (demon) hunter you won't need tape recorders as much as you will need a good Bible and alot of prayer. It's souls that the spirits want and any and every deception that can be propogated to capture the attention or torment the mind is used. In fact some of the most powerful spirit don't bother driving people mad, they make people wildly succesful. Are all successful people so influenced? No, but some are. Are you familiar with Christian demonology?