123. At 1435 ZT on 27 April, in DR position LAT 51° 56.8' N, LONG 150° 37.7' E, the Moon's upper limb is observed on the visible horizon, bearing 242.2° psc. Variation is 2° W. What is the deviation?

The deviation is 2.2 W. Compass error is the difference between the true bearing and the compass bearing; deviation is the compass error after accounting for variation. Solving for deviation requires subtracting the variation from the compass error, resulting in a deviation of 2.2 W.