Originally Posted By: MichaelJ07

I am always wondering how far the light from a signaling mirror travels. 5 miles? 25 miles? Do you have any info on this?

Yes: lots of info and personal experience.

It's very much a function of how clear the air is.

In clear air, 25 miles for a 2"x5" glass aignal mirror, and 45 miles for a 3"x5" signal mirror are about nominal for naked eye visibility - I've done that several times. In reasonably (but not overly) smoggy air - half that.

Range is greater when signaling toward the sun, less with the sun at your back.

Here are videos I made of the mirror flashes from my 3"x5" glass mirror at ranges of 0.7, 11.1 and 43 miles: http://www.youtube.com/watch?v=GwCbgQGmID4

A post on some of my 22-mile testing, with links to videos of the testing I posted on YouTube, are here:
Signal Mirrors at 22 miles: glass, metal, plastic

More references:
US Navy Test: "Mirror Flash seen 45 Miles"
Doug Ritter's Consumer Alert: "Phony Glass SIgnal Mirrors"
WWII U.S. Government Signal Mirror training film

BTW: My avatar image is a photo taken through the aiming grid of a signal mirror - that bright spot isn't the sun itself, but the virtual image of the direction the reflected light is going, produced by the retroreflective beads on the aimer mesh.

Edited by rafowell (11/06/10 06:14 AM)
Edit Reason: Explained avatar
A signal mirror should backup a radio distress signal, like a 406 MHz PLB (ACR PLB) (Ocean Signal PLB)