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Mk5 Stadimeter Analysis of how it works.
1. Operating range: Height or width 50 to 200ft, Range 200yds to 10,000yds = 600ft to 30,000ft (about 5nm)
Largest angle to be measured = 200ft at 200yds range = tan-1 200/600 = tan-1 0.3333 = 18.4 degrees or angle between mirrors of 9.2 degrees (maybe).
Smallest angle to be measured = 50ft at 10,000yds = tan-1 50/30,000 = 0.003 degrees = 0.18 minutes or an angle between mirrors of 0.9 minutes (maybe).

Now if we set the distance drum to 200yds say, as we slide the drum carriage along the height scale to the right, in other words look higher, the actuate arm will be pushed up and the angle between the mirrors increase, which is what we would expect.  However, it would be unwise to go any further without checking if the horizon mirror does not also move, there’s an awful lot covered up on the left-hand side.

Now we must turn to Martin Caminos.  Martin, do you still have your Mk5 stadimeter handy?  If so, please will you advise us which mirrors swivel and how they are connected?  We’re maybe looking for an adjustable four bar gate.  Many Thanks DaveP