Graphical Ray tracing on Hangar Floor

I am looking for a photo that shows optical engineers in some of the
large hangars doing optical design of a bombsight?

The folklore goes that they were using chalk on a string to draw the
radii of the lenses and then using chalk snap line strings to make the
rays on the floor of the hangar. The reason is that a large scale ray
trace might have been more accurate and/or much quicker than looking up
angles in trig table books. This was of course pre computer and pre
calculator.

If you have any photos or details that would be very helpful.
If you were there lets talk.

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