NavList:

The strangest Nav exam question that I can remember involved the ex-meridian. This required table 29 and 30 lookups in Bowditch to correct an observed altitude near meridional passage to get the actual meridian altitude (Bowditch calls this reduction to meridian). Never used this method outside the exam room and felt that it was a curious antiquated celestial technique. Table 29 is entered with the nearest whole latitude and declination to get the one minute altitude rate of change(a). The one minute rate of change(a) and meridian angle(t) or minutes to transit are used to enter table 30 for the correction in minutes of arc to be added to the observation(Ho) to get an upper transit altitude. Table 30 covers observations made within 28 minutes of time either side of meridional passage.

Greg Rudzinski
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