Peloris for Adjusting Ships Compasses

Home > Worthopedia – Price Guide > Fine Art >

Terms and Conditions for using our site

Peloris for Adjusting Ships Compasses

Sold For:

or Sign In to see What it's worth.

Sold Date: 01/10/2008
Channel: Online Auction
Source: eBay
Category: Fine Art

The instrument being auctioned is a pelorus. A pelorus is used to establish a ship's heading based upon the bearing of the sun. Critical to this determination is the sidereal (Sun) time and the sun's azimuth for that time which was provided in a reference book called Suns Red Azimuth tables.

This instrument belonged to William F Tribble, one of the most famous compass adjusters operating out of New York harbor in the late 19 th century and the first half of the twentieth century. During the 50+ years of his work he adjusted more than 15,000 ships compasses with this instrument. And, during World War II, he did as many as seven ships per day when normally he would adjust only one or two. All the Standard Oil Company ships were among his many regular customers. He also adjusted compasses for many famous yachts . One of the most notable was Gerald Lambert's Atlantic before her record breaking trans-Atlantic passage under the command of Charlie Barr.

Born in Mystic CT in 1867, Mr. Tribble was the son of a local ship owner, J. Frederick Tribble. An early mention of Mr. Tribble appeared in an article in the New London Day newspaper reporting on his excursion to Havana as the navigator of William Randolph Hurst's yacht Buccaneer sent to Havana to cover the crisis in Cuba that led to the sinking of the battleship Maine and thence the outbreak of the Spanish American War.

This instrument is as Mr. Tribble used it to adjust his last ship's compass upon his retirement in 1950. However, the instrument has been disconnected from the portable tripod that was used to secure the instrument to the ship's deck when in use. The pelorus has been remounted on a small round stand suitable for display on a table or bookshelf.

A copy of the "Handbook of Magnetic Compass Adjustment" prepared by the National Geospatial-Intelligence Agency is included for the buyer interested in learning more about the lore of this now dwindling art. themselves. is how the winning bidder can use this pelorus to establish true north just as was done by Mr. Tribble when adjusting a ships compass.

In normal usage, the compass adjuster would know his vessel's position and using the Nautical Almanac and Sun's azimuth tables he would compute the sun's azimuth for the time of the sighting. However, for casual use of this instrument, the simplest way to obtain the sun's azimuth, one day at a time, is to utilize the US Navy's Hydrographic Office azimuth calculation website. you will get the answer without having to refer to the tables. Go to:

http://aa.usno.navy.mil/data/docs/AltAz.php

For any given day you enter the name of the closest city ( in lieu of your actual position) on the website form. Your computer will have entered the current date. With these inputs, the website will provide, as output, the altitude (Alt) and azimuth (Az) for the entire current day in 10 minute time intervals. Print the output.

You are now ready to find true north. Set up the instrument with a clear view of the sun, note the current time and sight the sun through the azimuth vanes. Now, holding the sun in line, turn the instrument's azimuth circle to the azimuth provided by the website for the time of your sighting. The instrument's north symbol will now be pointing to True North.

Opening bid: $ 395