optical range finder

Prepare to be Be-Dazzled Part 2 - The Optical Range finder

The Cannons in Hopewell Cape used to be painted in Dazzle Camouflage to disrupt the Optical (Coincidence) Range Finder. Which was developed by an American in 1890. The range finder is basically a pair of binoculars, with the eyepieces normal distance apart, but the objective lenses spaced very far apart. Such that when you look through the device at, say, a German Battleship, you see an image that looks like the one to the right.

Note that the very top of the mast is off by just a tad--the images from the two objective lenses do not quite match up. The range-finder operator then adjusts the knobs on the range-finder until the mast lines up exactly. See figure to the right. 

By some very basic trigonometric principles you can then calculate the distance to the target to a very high degree of precision. Note that in order to use the device properly, the operator needs to have a good idea of what, exactly, he is looking at so he can match up the images properly.

Once the Americans came up with this, every major power at the turn of the 20th c. invested in it even further, and all the major powers used range-finders to guide their naval guns and field artillery. Next week we'll introduce the invention of dazzle camouflage. 

Now that's a story worth exploring!

The Victory Cannon Campaign is raising funds to restore the two captured World War One cannons situated in the square in Hopewell Cape. These cannons were captured by Canadians during the Great War, and were awarded to the people of Albert County. You can donate online to the Victory Cannon Campaign here, and best of all you'll be sent a tax receipt!  Click Here to Donate!