Because the core of the reflected sunbeam from a flat signal mirror is very narrow, all rescue signal mirrors must include an aiming system. The rearsight aiming system of the signal mirror sold by Dive Gear Express uses a double-sided reflector with a central hole. Such signal mirrors are easy to use, but you should practice aiming to be better prepared to use it in an emergency:
- Hold the instruction side of the mirror approximately the length of the mirror itself from your eye, and face the mirror halfway between the sun and your target.
- Catch the spot of sunlight passing through the central hole on your face, hand, or other surface (the whiter, the better).
- Tilt the mirror so you see that spot reflected in the rear of the mirror.
- Using one eye, sight your target in the very center of the central hole.
- Tilt the mirror so the very center of the spot reflected on the rear of the mirror repeatedly crosses back and forth across the very center of the hole.
- For more help aiming double-sided signal mirrors see the following:
For background on signal mirror aiming methods, see the U.S. Search and Rescue Agency Air Sea Rescue Bulletin (pages 6-11) that includes descriptions of the reflex, rearsight, foresight, and improvised foresight methods along with results from a joint field test by the US Coast Guard and National Bureau of Standards.
Guest authored by R. A. Fowell under license (CC BY 4.0)