Originally Posted by
Penny Washers
IMHO, that rangefinder is the wrong way round. Should not the two lenses close together form the eyepiece? So what is the second girl doing?
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Well spotted, PW. Although the Imperial War Museum list this device as "Telescope, Identification, AA, MkIII (
Rangefinder, cased)", if you read the 1938 instructions
here there is no mention of any rangefinding going on at all. In fact, it is two telescopes laid end-to-end; the junior ATS girl would pick up the intruder using the low-power telescope, then the senior ATS girl would identify it using the high-power side, and the azimuth and elevation would be read off and passed to the central computer (human!).
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"Why are there two eyepieces, Ethel?"
"It says here it's to avoid delay if either operator happens to be powdering her nose when an intruder approaches."