80 HANDBOOK OF MAGNETIC COMPASS 



109. C. Final compensation at sea. — {Compensation and final de- 

 viation data are best made with the coils energized to their operat- 

 ing conditions for at least 20 minutes. If any coil requires securing 

 hy reversals^ it should he so secured each time during the process of 

 compensation.) 



1. Purpose. 



(a) The final compensation is made at sea after the mag- 

 netic adjustment in order to improve any degaussing 

 deviations still existing as a result of inaccuracies in 

 the dockside compensation from : 



(1) Dockside interferences. 



(2) Movement of the soft iron correctors as a result of 



magnetic adjustment. 



(3) Inaccuracies of dockside deflection methods 



(4) Poor coil alignments. 



(5) Poor directive force on the unadjusted compass at 



the time of dockside compensatjion. 



2. Compensation. 



(a)- The different coil compensations are made individually, 

 with maximum operating currents^ and on the same 

 headings as previously described under article 108. 

 The differences in this case are (1) the ship is actuallj' 

 placed on the compass headings, rather than by de- 

 flection of the compass card to the desired headings, 

 and (2) the degaussing coils are successively ener- 

 gized on one heading, compensating the deviation of 

 each degaussing coil individually until all degauss- 

 ing coils are on. All degaussing coils are then se- 

 cured and the ship placed on a heading 90° from the 

 previous heading and the procedure repeated. 



3. Deviation curves. 



{a) After refinements are made on each coil compensation, 

 and everything is physically and electrically secured, 

 a deviation curve is taken with the degaussing coils 

 at the proper current settings., as indicated on the 

 degaussing chart. This deviation curve is in addi- 

 tion to the normal undergaussed curve, covered in 

 articles 89, 126, and 132, and should be recorded as 

 such on the standard Navy Form NBS 1104 or 1105, 

 as well as in the Compass Record Book. Condi- 

 tions of coil current settings are all recorded on Navy 

 Form CC-1. 



