Method and apparatus for precise calibration of magnetic compass and preparation of deviation tables

An apparatus for compensating for deviations between the reading of a magnetic compass and the true bearing of a vessel, the apparatus comprising:

• a mounting plate for a compass rose, said mounting plate having an index line which is congruent with or parallel to the center line of said vessel and means for leveling said mounting plate to provide a level surface for a compass rose and an axle for a compass rose along said index line;
• a compass rose whose center is at said axle and which is calibrated in units the same or readily convertible to the units of a magnetic compass to be compensated, said rose further being capable of alternately being rotated or fixed in position about said axle;
• and
• solar aiming means, said solar aiming means providing means for precise alignment of an index about said axle as necessary to precisely fix the position of the sun at a given time, said solar aiming means further comprising a reading arm which may be rotated about said axle and which comes to a point upon said compass rose calibration, and a solar aiming arm, said solar aiming arm being mounted or attached to said reading arm so that said solar aiming arm may be rotated both in a plane which is perpendicular to said rose from a hinge upon said reading arm at or near the opposite reading arm end from said point and includes the line from the compass rose center and said reading arm point and also may be rotated together with said reading arm about said axle until said solar aiming arm is pointed directly at a target, such as the sun.