Osborne Fire-Finder at Dawn

[MLAA]

1. For the rare person who, like me, had no idea what the Osborne does 😬

The system is composed of a topographic map of the area oriented and centered on a horizontal table with a circular rim graduated in degrees (and fractions). Two sighting apertures are mounted above the map on opposite sides of the ring and slide around the arc.


A USFS Fire Lookout using an Osborne Firefinder while on duty at Vetter Mountain, California.
The device is used by moving the sights until the observer can peek through the nearer sighting hole and view the cross hairs in the further sight aligned with the fire. The fire lookout notes the degrees on the graduated ring beneath the sight. Early Fire Finders were capable of a crude estimate of elevation based upon the level and elevation of the table, calculating distance and rough position of the fire by reference to any distinctive terrain features and by use of the s