from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A fixed compass card on which bearings relative to a ship's heading are taken.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A device used to take a bearing on a distant object.
from the GNU version of the Collaborative International Dictionary of English
- n. An instrument similar to a mariner's compass, but without magnetic needles, and having two sight vanes by which bearings are taken, esp. such as cannot be taken by the compass.
from The Century Dictionary and Cyclopedia
- n. Nautical, an instrument for detecting errors of the compass by the bearings of celestial objects.
Second, it must be remembered that the bearing of any object obtained from the pelorus is the bearing _by compass_.
Two pelorus repeaters swung to point a few degrees right of course.
Light clusters, clear, deep, on the face of the radio gear ... fans up softly off the dial of the pelorus ... spills out portholes onto the white river.
Steady the ship on this heading until the shadow from the pelorus vane at the proper L.A.T. cuts the circumference of the pelorus dial at the proper magnetic bearing.
All being ready, secure the lubber's point of the pelorus at North and clamp the sight vane to the sun's magnetic bearing at the time you have figured to take the first heading.
Starboard or port your helm until at the time calculated the reflection of the sight vane on the pelorus dial cuts on the proper magnetic bearing.
If there is any Deviation on this heading, adjust the cast iron cylinders (called Quadrantal Correctors), which are on each side of the compass bowl, by moving them toward or away from the compass until the ship's head by compass is North-east at the proper time and bearing by pelorus.
If you set your pelorus, so that it will exactly coincide with the course you are steaming as shown by the compass in your chart house and then get a bearing of the sun by noting where the shadow from the pelorus vane cuts the circumference, this bearing will be the bearing of the sun by compass.
The easiest and most accurate way to find the error of your compass is, first, to find the bearing of the sun by your pelorus.
If, now, the compass were correct it would agree with the pelorus in showing the ship's head to be North.