Underwater magnifying glass

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Anybody have any experience with a Pratt Macrosnooper? It is a DIY underwater magnifying glass refered to briefly in the NOAA diving manual.

 

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OK, I guess nobody has tried it so I'll give it a shot.

This is the exert from the NOAA manual:

At the other end of the magnification continuum is an
underwater magnifying system (Pratt 1976). This device,
referred to as the Pratt Macrosnooper, has a magnification
power of seven and permits the diver to study marine
organisms too small to be comfortably observed with the
naked eye. It is a three-element lens system designed specifically
for use under water and consists of three lenses with
appropriate spacers inserted into a 2-inch (5-cm) plastic pipe
(see Figure 9.7). Holes are then drilled through the housing
and the spacers to permit the entry of water for equalization
at depth. When in use, the Macrosnooper is held against
the mask faceplate. It should be cleaned and rinsed carefully,
along with other diving equipment, after each use. Soap,
mineral, or fungus deposits may be removed by an
overnight soak in either diluted bleach, vinegar, or laundry
detergent.

And maybe the pictures: