Weeks after I asked the ballistic math questions, I got this email:
Was intrigued by your trig problem.
Herewith my answers:
1) take distance and bearings at regular intervals, say 20 seconds apart. (take bearing and ten seconds later take distance, repeat for 1 minute. Using change of bearing and distance, plot 1 minute of travel; use of graph paper expedites solution for speed and direction. Alternately, use similar triangles and trig functions to calculate.
2) from cannon bearing 18.33 degrees at 7.74 km.
3) after 1 minute of travel, the cannon should be laid to 23.00 degrees at 7.50km.
4) 1 MOA at 7500 meters is a bit over 2 meters dispersion. If one assumes that both horizontal
And vertical dispersion are the same, which is NOT usually the case with arty, then the area inside the impact zone is about 4 square meters. Given the projected area of the ship, a hit ought to be a certainty.