The Marine Sextant, Continued
An example of a reading of negative index error is shown in figure
8-18. Notice that the index mark is to the right of the 0 on the arc scale
and the 0 on the vernier scale is below the 0 on the micrometer drum.
The micrometer scale and vernier scale line up directly on the 0.7' mark
of the vernier scale, indicating a -0.7' index error. The correction would
be added to any angles shot with the sextant.
Figure 8-18. Negative index error.