Ross Stereo Telescope (!)

Binoculars are really good at giving a sense of perspective, or depth in an image, particularly when looking at garden birds or whatever else is in the undergrowth… so a Stereo Telescope should be much better, shouldn’t it?

In military circles, the problem is that the enemy is much further away, particularly when you are worried about artillery ranging to a target. The problem is always estimating the range of the target from the weapon, and then in estimating how close the last shot landed – does the range need to be increased by 50 yards or 100 yards? In WW1 telescopes were used by spotters in barrage balloons, to direct the guns…. the elevation gave them the triangulation needed to make more accurate estimates of the position of the shots and the target.

Stereo telescopes were presumably a development of this technique, and possibly made their first appearance in WW1, but this example, made by Ross, appears to me to be more likely introduced between the wars, and was possibly used in WW2. Very little comes from searches on Google, although a video from explains the principle of operation, in that it extends the distance between the eyes of the operator by around a factor of 10x, so extending his own sense of binocular vision. The example they showed was of German manufacture, I believe: also on the web I found a photo of a German soldier up a stepladder using one of these for artillery ranging.

Description of this Ross model

This Stereo telescope, or binocular pair of telescopes, was acquired in 2010, and is Accession number 135. Undoubtedly military, in camouflage green, they come in the sturdy type of wooden box – on that you might have expected to find ammunition inside. The wood inside is covered with green baize, and contoured to fit round the instrument.

The “ammunition box” image and the broken hinge reflect very well on the size and weight of these binoculars, which are about 5.5Kg (12lbs). How the German soldier climbed his rickety ladder and then lifted up and used such a pair is not explained! They really feel that there should be a tripod, or at least a mounting point on the binoculars, but nothing is evident.

The two 30cm long arms of the dual telescope each form the barrel of one telescope:  on the ends the two “eyes” are the 40mm objective lenses, each having a 90 degree prism behind the lens so that they look out perpendicularly to the barrel axis. At the other end of each barrel there is another 90 degree prism directing the light through an eyepiece: the two eyepieces are two hinged halves of the central hub, where the observer can look through both eyepieces, positioned the correct distance apart to fit the operator’s face. There are two eyepieces available, presumably giving the different magnification powers.

Markings on the dual telescope

Most of the markings are on the rear face of the central hub, where they read as follows:

Stereo Telescope

X 10 & 20  Ø 4°

Ross, London

No. 83966

I interpret this second line as the magnification levels of 10x and 20x achieved thru the two sets of eyepieces, and the viewing angle seen through the scope, of 4 degrees. The serial number of 83966 I can’t believe was a production number of this type, it must have been a general construction number of all of Ross’s military hardware.

Use of the Stereo Binoculars

Being so heavy, they are very difficult to use without a suitable balustrade or wall to rest it on! Or a suitable stand.  Plus they would only really be useful looking at objects on the horizon or similar, so not much use trying to find a low flying aircraft!

If anyone has ideas of wanting to try them on some battlefield, I’d be delighted to pass them on!


  1. A similar Ross stereo pair, No 67695, was offered in a Barnebys auction in 2020 for £100.
  2. The German officer picture was described as: “A German Artillery officer using a stereo telescope at the top of an Artillery Observation Ladder, hidden behind a haystack”. From Rickard, J (1 October 2007), Stereo Telescope on Artillery Ladder,

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