20th Century Kelvin Hughes & Son Station Pointer

The 20th Century Kelvin Hughes & Son Station Pointer.
Figure 1: The 20th Century Kelvin Hughes & Son Station Pointer.
I've obtained this instrument in 1996 together with the Warren Knight station pointer in my collection. The instrument is used for coastal navigation using a sextant and was invented in 1801 by Joseph Huddart, a U.S. naval captain.1

This instrument, also referred to as a three-arm protractor, is composed of a circular scale connected to three arms. The centre arm is fixed, while the outer two can be adjusted to an angle previously measured with a sextant.

In coastal navigation the vessel's coordinates can be established by measuring two horizontal angles between three coastal objects. After setting the legs of the station pointer to these angles (adjustment is done with two drum micrometers, see figure 11 and figure 9) it can be laid on a map showing the same objects (see figure 2). With the legs running over the objects on the map, the centre of the instrument will be your position in it.

To mark the acquired position a cross bar with a small dent is available at the centre of the instrument (see figure 9), there are no additional tools as with the Warren Knight station pointer.

The Kelvin Hughes station pointer on a map of the Isle of Man.
Figure 2: The Kelvin Hughes station pointer on a map of the Isle of Man.
This protractor has serial number 1413 (see figure 11), but so far no manufacturing date can be determined from it. As Kelvin Hughes started in 1947 it must be more modern than the Warren Knight station pointer in the collection, possibly even from the 1960s.

Provenance
The Kelvin Hughes station pointer was once bought by Osiris-Ceso BV in the Netherlands (see figure 4).

Osiris-Cesco had started in 1965 as Dredging Investigations, a subdivision of Boskalis, one of the world's leading dredging companies. It was renamed Osiris Survey Projects in 1975 and became Osiris-Cesco in 1978 due to a joint venture with Fugro-Cesco. As the company sticker indicates Osiris-Cesco was a "Survey and Site Investigations" company. In 1988 they became Osiris Seaways Ltd, which I joined in 1989. It then became Osiris BV, and was sold to the French CGG (Compagnie Générale de Géophysique) in 1994. It finally dissolved into Fugro at the end of the 20th century.

Shortly before I left Osiris in 1996, I was given these two station pointers, which otherwise would have ended up in the skip.

If you have any questions and/or remarks please let me know.

The box of the Kelvin Hughes station pointer.
Figure 3: The box of the Kelvin Hughes station pointer.
 
The Osiris-Cesco label on the box.
Figure 4: The Osiris-Cesco label on the box.

The box of the Kelvin Hughes station pointer opened revealing its contents.
Figure 5: The box of the Kelvin Hughes station pointer opened revealing its contents.
 
The box of the Kelvin Hughes station pointer opened revealing its contents.
Figure 6: The box of the Kelvin Hughes station pointer opened revealing its contents.

The manufacturer's name on the circle of the Kelvin Hughes station pointer.
Figure 7: The manufacturer's name on the circle of the Kelvin Hughes station pointer.
 
A full view of the circle of the Kelvin Hughes station pointer.
Figure 8: A full view of the circle of the Kelvin Hughes station pointer.

Only a cross-bar with a central dent determines the center.
Figure 9: Only a cross-bar with a central dent determines the center.
 
One of the drum micrometers at 12°-17'-30".
Figure 10: One of the drum micrometers at 12°-17'-30".

The serial number of the Kelvin Hughes station pointer.
Figure 11: The serial number of the Kelvin Hughes station pointer.
 
The legs of the Kelvin Hughes station pointer are marked with dots.
Figure 12: The legs of the Kelvin Hughes station pointer are marked with dots.

Celestial Navigation Coastal Navigation Distance measurement
1942 station pointer 20th c. station pointer