RAF Old Sarum, Wiltshire Camera Obscura

95 - Camera Obscura.

The plan of RAF Old Sarum in 1932 showing a lot of its First World war hangars and buildings before the expansion scheme had started after 1932.

The Camera Obscura hut behind I think the oil instillation.

Camera Obscura hut entrance and one shuttered window.

The Camera Obscura was a teaching aid to bomber pilots to hone their skills on before they go to drop on the ranges and then to war. A simple method of just skilful flying over the target airfield, then pin pointing the target building (the Obscura) and flashing a very bright light. The flash would be seen on the table and the accuracy checked and related to the pilot. Later on the Air Ministry used an Air Ministry Laboratory to do the same job, inside a specially made building.

The Camera Obscura in the roof.

A square lid on the roof would slide back allowing light through the lens onto the table.

Drawing Number AP1243S.

This is a drawing of an AP1243A Camera Obscura showing the layout of the building. The same apparatus, i.e. the frame and lens, can be used in a tent. Plan AM 3391/35 depicts a rectangular building 20ft x 10ft with two shuttered windows, one on each end wall. Part way down one wall is a 'Cat Ladder'. A sliding wooden cover 4ft 6inch square is mounted on rails on the roof next to the aperture. Originated from AIX

The following is gleaned from “I Saw Two England´s” by HV Morton, published in 1943 by Methuen & Co. Ltd., London, and Reginald Saunders, Toronto. Morton toured England in early and late 1939. On his second tour, shortly after the beginning of the war he gave an account of a visit to the Royal Air Force Flying Training School. The following is an account of a method of training bomb-aimers: “Another ingenious invention is the camera Obscura hut, which tells the instructor whether a man in a bomber several thousand feet above him, has, in theory, bombed the hut. The place is dark save for a circle of light reflected (projected) upon a table through a lens in the roof. A spot in the centre on the table represents the hut" . “When an aeroplane is flying overhead you can watch its shadow (image) slowly cross the table, as it is reflected (projected) by the lens. As it nears the centre a tiny white flash is seen, which is really the firing of a magnesium bulb in the aeroplane. This represents the bomb, or rather the exact moment at which the bomber pressed the bomb-release". “The instant the flash is seen, it is plotted on the table. It is a simple matter to allow for the time taken for the bomb to drop according to the height of the plane, the angle at which it falls, according to the speed and wind, and this shows you how near, or how far, the bomber was from his target”.
(words in brackets are mine – SW).
This article was originally distributes as HVM Society Snippets – No.165; 29 March 2014.