Why amplitude of moon is not taken ?

1. Due to large parallax – The time when noon’s centre is at the rational horizon. The upper limb should be touching the visible horizon, very difficult & great error possible.
2. Change of dec is very jast – minor change is miscalculated GMT would lead to large error in amplitude correction.
3. The moon is not always readily available – for observation, depending upon the clarity or visible horizon, the phase of moon and time of moon – rise set.

Procedure for amplitude problem  :

1. Find the LMT from the nautical almanac daily page for rising or setting.
2. Got GMT by applying LIT with LMT
3. Extract declination from almanac against date & GMT
4. Get amplitude by using the formula, Sin amplitude = Sin dec X sec latitude.
5. Find true bearing from amplitude.
6. Difference b/w True & Gyro will be gyro error.
7. If necessary find deviation also.