What are these binocular periscope type things?

Factual Questions
1

So, I’m passing a typical Saturday night, sat at home watching an old sci-fi film, in this case Crack in the World (quite good, apart from its ludicrous premise, obnoxious hero, and a certain amount of “Run! Run! If that deadly lava flow breaks out of the back projection, we’re all doomed!”).

Anyway. At several points in this film, people are watching things like nuclear explosions and erupting volcanoes (from a darn sight closer than I’d like to get, I can tell you), and they are using these peculiar-looking gizmos: a tripod stand, on which is perched what looks like a pair of small periscopes - lenses on tubes, with a binocular eyepiece at the bottom. They seem to be adjustable, so you can have the two tubes parallel, or splayed out in a V shape. I’ve seen these in other films of the same sort of theme and era (seem to recall them from War of the Worlds), but I’ve no idea what they might be used for. A periscope might be a good idea for watching explosions and so forth, so you can cower in a hole in the ground and still watch the mass destruction - but why the two tubes, and the adjustable thingy?

So, my question is, what are these things called? (If they turn out to be “binocular periscopes”, I’m going to be embarrassed.) And what are they for? Other than to look vaguely scientific-equipment-like in these sorts of films, that is.

2

I think those are rangefinders, which are used for artillery. Binocular vision allows the user (with markings in the viewfinders) to determine the range to a target. In WWII the Germans had a version that looked like a tube about a metre long with the lenses on the sides at the end. The “periscope” type would have the advantage over those in that the user could remain under cover. (Although I wonder how close the artillery would be. Close enough to worry about rifle fire?)

I’m not an expert, but that is what I’ve always assumed they were: periscope rangefinders.

3

Ta muchly. Sounds plausible enough to non-military me… but what’s the advantage in the adjustable V-shaped arrangement? Widening the field of view?

4

The further apart he two view points are, the easier it is to get an accurate distance fix by triangulation.

5

and I would imagine that the adjustable/folding aspect is just to make the apparatus easier to pack away.

6

Yep, they are an artillery spotting scope. The US Army only uses them in training as far as I know. When I was in the Army we just sat in a foxhole with Binos and PRC-77. I think that were used mainly to avoid being sniped.

7

Well, next time I see one of these things, I’ll know what it is. Thanks, folks.

(Though one thing worries me… john_e_wagner’s explanation that they’re used to avoid being sniped, and only used in training. Is sniping at trainees a problem in the US Army? Mind you, I remember the way I used to feel about undergraduates when I was teaching… )

8

john_e_wagner mentioned encountering them only in training probably becasue they had been withdrawn from use in most units but in training, any equipment that a soldier may encounter is often covered, even if only National Guard and Reserve units still use it. Stadiametric (comparing marks in the optics to heights of objects observed) and coincidence rangefinders have mostly been replaced by lasers in military usage. The stadiametric method is still taught, since you don’t need a power source to operate a pair of binoculars but it is not the ideal method.