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.


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