CORRECTOR EFFECTS 



63 



bar is due mostly to compass needle induction since the bar is small in 

 cross-section and is close to the compass. Since such needle induction 

 is practically constant, the deviation effects on the compass will change 

 with magnetic latitudes because the directive force, ZT, changes. How- 

 ever, when balanced by sphere correctors this is advantageous because 

 it tends to cancel out the variable part of the sphere correction which 

 is due to the compass needle induction. 



94, Slewing of spheres. — Figure 33 is a convenient chart for deter- 

 mining the proper slewed position for spheres. The total values of 

 the D and E quadrantal coefficients are used on the chart to locate a 



5FHERE Chart 



Figure 33. 



point of intersection. This point directly locates the angle and di- 

 rection of slew for the spheres on the illustrated binnacle. This point 

 will also indicate, on the radial scale, the resultant amount of quad- 

 rantal correction required from the spheres in the new slewed po- 

 sition to correct for both the D and E coefficients. The total D and E 

 coefficients may be calculated by an analysis of deviations on the un- 

 corrected binnacle, or by summarizing the uncorrected coefficients 

 with those already corrected. The data in figures 31 and 32 will be 

 useful in either procedure. For further information concerning 

 slewing of spheres see article 139. 



Examvple: A ship having a Navy Standard binnacle, with 1" spheres 

 at 13" position athwartship and 12'' Flinders bar forward, is being 

 swung for adjustment. It is observed that there exist 4° E. D error 

 and 6° E. E error with the spheres in their existing positions. Since 



