Calculation: sextant altitude Hs to apparent altitude Ha to correct the sextant’s inherent errors and the error induced by the height of the eye (Dip) above the horizon. (Altitude = Height)
This page contributes to the primary objective of offering guidance and interactivity on the calculation and understanding of the Line of Position (LOP) using only a sextant and the sun, and then tracing this line on a plotting sheet. See recommendations.
On this page, we will learn how to calculate the apparent height of the sun. However, I recommend first reading the theory of apparent sextant height.
sextant altitude to apparent altitude: On this page
Calculating Hs to Ha:
(The Dip error is always negative !)
sextant altitude to apparent altitude: example
How to calculate apparent height (Ha)
The entries:
sextant altitude
Hs = 74° 06′
Index error
Index error = + 0° 07′
Non adjustable error
Hs = 74°06 is about 75° so the error is +1′
Non adjustable error = + 0° 01′
ε = non-adjustable error + index error = + 8′
eye height (Dip error)
DIP = – 0°02′,5 = – 2′,5 (eye height = 2 meters)
DIP of the horizon: see altitude correction table
ALTITUDE CORRECTION TABLE:
sextant altitude to apparent altitude: solution of the example
sextant height (Hs) to apparent height (Ha)
Hs …………………..= 74° 06′, 0
ε ………………….. = + 00° 08′, 0
Dip………………… = – 00° 02′, 5
_________________________ +
Ha…………………. = 74° 11′, 5
sun correct LL ….= _ _° _ _’, _
__________________________ +
Ho…………………….= _ _° _ _’, _
