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And just to triple check my computation, HO 214 produces 66° 13.7' and 292.6. I programed a Casio PB-1000 calculator 30 years ago, to do celestial and great circle computations. Enter departure and destination coordinates and it calculates initial GC course and distance, rhumb line course and distance and vertex. Then select inertmediate longitudes or increments and it calculates the intermediate waypoints, the rhumb line course and distance between the waypoints, totals all the rhumb line distances and tells you how many extra miles over the perfect GC distance. 

50° 43.3'N 127° 29.6'W

to 

53° 53.4'N 166° 32.5'W

CG distance 1426.6 nm, initial course 292.9°, RL distance 1444.6, RL 18.0 nm longer than GC track, course 277.6°,  vertex 54° 20.3'N 156° 20.1'W

130° W 51° 21.5'N, RL102.0 nm ,292.0°

150° W 54° 10.8'N, RL 745.2 nm, 283.1°

160° W 54° 16.7' N, RL 350.8 nm, 271.0°

166° 32.5' W 53° 53.4' N, RL 231.4 nm, 264.2° 

Total RL distance 1429.4 which is 2.8 longer than a perfect great circle track.

Since the rhumb line is only 18.0 nm longer than a perfect great circle would it be worth doing especially if it takes you into high latitudes or other hazards?

gl