Enter the index error and the observed altitude into the calculator to determine the corrected altitude. This calculator helps in adjusting celestial navigation observations for any index error present in the sextant.
Vertex Correction Formula
The following formula is used to calculate the corrected altitude.
CA = OA - (IE / 60)
Variables:
- CA is the corrected altitude (degrees)
- OA is the observed altitude (degrees)
- IE is the index error (arc minutes)
To calculate the corrected altitude, subtract the index error (converted to degrees by dividing by 60) from the observed altitude.
What is Vertex Correction?
Vertex correction is the adjustment made to the observed altitude of a celestial body to account for the index error of a sextant. The index error is the angular displacement between the zero of the vernier scale and the zero of the arc, which occurs when the sextant’s mirrors are not perfectly aligned. This error must be accounted for to ensure accurate celestial navigation.
How to Calculate Vertex Correction?
The following steps outline how to calculate the Vertex Correction.
- First, determine the index error (IE) in arc minutes.
- Next, determine the observed altitude (OA) in degrees.
- Next, gather the formula from above = CA = OA – (IE / 60).
- Finally, calculate the Corrected Altitude (CA) in degrees.
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
index error (IE) = 2 arc minutes
observed altitude (OA) = 45 degrees
