[Chock]

The standard Aldis sight did indeed not have any magnification, but the original 1915 version (made by Aldis Brothers of Birmingham) did magnify the view (featuring x3 magnification). That version was the one originally evaluated at Martlesham Heath by sticking it on a BE2 with a Lewis gun. It was indeed proved to be more accurate than the ring and bead site, however, an early pointer to the problems it could cause was the fact that more than one of the test pilots almost flew into the ground whilst using it (they were testing it by firing at ground targets). Having determined that, the tests went on to evaluating it in the air, and it was at that point that it was determined the magnification factor was unhelpful and that it was a good sight, so the ones later produced en masse did not feature magnification, but instead had graticule markings for range finding and deflection. 200 of these were ordered from Aldis. Another problem was that it oiled up, easily, so a subsequent modification was a flip up front cover, much like you find on telescopic rifle sights these days, which was operated from the cockpit by Bowden cable.

It eventually evolved into what might be regarded as the 'standard' Aldis sight, being just short of two feet long (22 inches) and in there were four collimating lenses with an inert gas inside the tube. The actual sight picture had two rings on it, one of which was matched to indicate the wingspan of a Gotha twin engined bomber at 200 yards, which gives one an idea of the sort of ranges you could expect to start firing with an Aldis sight. The inner circle was supposed to assist deflection shooting, when compared with the position of crossing targets at 100 mph touching the outer ring marking. Although it did have a rubber eyepiece, it was usable when the eye was placed about 5 inches away from the lens, which gives you a 20 degree field of view.

Al