Sometimes it is not possible to obtain sextant altitude of the celestial body when it is on the meridian due to clouds, hazy horizon, rain or other reasons. The celestial body is then observed when it is near the meridian. The value of Ex-meridian limits are obtained from the nories tables OR as an estimate, if the Latitude and Declination are the same name then subtract the value and if different names than add the value, the value obtained will be the value of limits in minutes before and after meridian passage for taking sight. This is called Ex meridian limits. Within this window period one should obtained the sight of the celestial body when it is near the meridian.Also read this - What are the types of antenna and aeriels used onboard the ship?
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