NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Brad Morris
Date: 2019 Mar 7, 11:18 -0500
Here is another missed CN opportunity. I cheated and recorded my gps position and then used google earth to determine my distance off.
Distance 1.5 nm.
From Bowditch (1958 ) table 22 for a height of eye of 50 ft the dip is 19.5'.
Looking at the table the dip is relatively insensitive to distance off but is very sensitive to height of eye. Unfortunately I have no idea of my height of eye. It is a complete guess.
Height Dip
40 ft 15.7'
50 ft 19.5'
60 ft 21.4'
70 ft 27.0'
Ideally I would perform a reverse distance off measurement when the ship is berthed to determine the height of eye. Unfortunately (again) I cannot think of anywhere I could take such a measurement.
This particular ferry has an open observation deck at the bow in front of the bridge. Views are clear through a 180 deg arc. Despite its location it is reasonably shelterd from he wind. A good spot for CN. If the Master saw me with a sextant maybe he would invite me up to the bridge!!!!!!!!
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