[John Pancoast]

Originally Posted by FUBAR295

Here is the UBoat Commanders word on the periscope.

Good hunting,
FUBAR295

130.) For computing the range, the 1 magnification should be used in the periscope. With the 6-fold magnification, no estimation of distance is possible, on account of the monocular optical system of the periscope.

As a matter of principles the 6-fold magnification of the periscope should always only be used temporarily, in order the better to observe details of the enemy ship, as, for example, in computing its course and speed, but never for the actual attack at close range.

or derstosstrupp's retranslation :

130.) In estimating range, always use the 1.5x magnification in the periscope. The monocular optics of the periscope do not allow for range estimation at 6x magnification.

The 6x magnification of the periscope basically may only be used temporarily in order to better observe details of the enemy ship, for example in estimating angle-on-bow and speed, however never for conducting the actual close-range attack.

That's what I was referring to, thanks !