How many number of Stars required to find ship’s position ?

  • Abnormal refraction causes an angle between the true direction and apparent directions of the body as a result of which the body could appear higher than their actual altitude.
  • As temperatures around the Red sea are very high, the altitudes of a body can be affected by refraction as it depends upon temperature and pressure of the atmosphere.
  • Nautical tables have table giving mean refraction based on standard sea level and pressure values .
  • Refraction changes values of “dip” as refraction can also alter a visible horizon.
  • Possible dust can create incorrect visible horizon.
  • Low coastline can be mistaken as visible horizon.

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