Most Frequently Used Naval Navigation/Piloting Instrument

[dgurgel]

When a naval vessel is within a few miles from land approaching a port, the most frequently used instrument is the pelorus. See
http://www.marinecompasses.co.uk/p144/A ... ount).html.

A pelorus on each bridge wing and one amidships permit the officer of the deck and navigator to quickly "shoot" the bearings to two or three visual landmarks (buoys, points of land, steeples, etc) and then plot a fix on a chart. A naval pelorus has a gyro repeater (slave compass) on the face; but a relative bearing on a fixed, dumb, compass ring will do; just add the relative bearing to the ship's heading. (And of course correct for the compass deviation from true north.)

Movable pelorus sighting vanes on the face of the gyro repeaters are aimed at the object in the same manner as rifle sights. True bearings are read directly by observing the degree on the compass card with which the crossbar of the sighting vane lines up. Relative bearings may be read from an outer dumb compass ring on the pelorus stand.

Even today, close to land in clear weather, the one driving the ship (the office of the deck) depends more than anything on visuals sightings taken with the pelorus plus channel buoys and other aids to navigation. The pelorus also is used to to check for collision hazards. As all know, a contact on a steady bearing with decreasing range is on a collision course.

Now that naval vessels have GPS, the pelorus (along with the chart) is still is the instrument of choice close in during daylight hours. On my recent first significant Albin transit I missed not having a pelorus.

The pelorus on the referenced web site is available from several overseas merchants; but I have not found a U.S. store. I am putting it on my Christmas list.

[DougSea]

Hi Dave,

Interesting bit of info there. All this talk on the forum recently about "what would you do" has me interested in alternate navigation plans and methods.

I looked around a bit for you, this was the closest I could get: http://www.celestaire.com/Compasses/Pro ... lorus.html

It looks like the same brand (Autonautic) so perhaps they could source it for you.

[dgurgel]

Thanks, Doug. That is the one. I plan to buy one if they also have the mounting base.

[joe.baar]

One thing I miss aboard our Albin is having enough knowledgeable crew to do stuff like this. As on my Sea Explorer ship so many years ago, and on any naval vessel, someone is always available for these tasks.