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…………………….= _ _° _ _’, _