Most of these units can be used as a rugged handheld thermal imager or without the daytime scope to give the shooter more options.
Heat signatures in inanimate objects such as trees, rocks and manmade structures are attained by absorbing heat from the sun. Living things such as humans and animals create their own heat internally, as do vehicles and aircraft. Because different materials absorb and lose heat at different rates, they render a distinct pattern and signature when rendered through a thermal imager. As a device, thermal imagers are as usable during the day as they are at night time.
When mounting a clip on unit, they must go on in front of the optic as a clear pane of glass or scope lens in this case, will act as a mirror and render the thermal imager useless.
Choose from Armasight, ATN or FLIR for a variety of options to turn your rifle into a true day or night system.