- 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.
- Change of dec is very jast – minor change is miscalculated GMT would lead to large error in amplitude correction.
- 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 :
- Find the LMT from the nautical almanac daily page for rising or setting.
- Got GMT by applying LIT with LMT
- Extract declination from almanac against date & GMT
- Get amplitude by using the formula, Sin amplitude = Sin dec X sec latitude.
- Find true bearing from amplitude.
- Difference b/w True & Gyro will be gyro error.
- If necessary find deviation also.

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