Humboldt State University ® Department of Chemistry

Richard A. Paselk


Photos of Navigation Instruments and Model Instruments

Richard A. Paselk

(The labeled photos below were created for a couple of articles I wrote in 2006-2007)

Click on the pictures for larger images. Additional images are available via the links.

English vernier sextant, c. 1900

sextant photo icon

sextant photo with parts labeled icon

Description: Brass construction with black oxidized frame, index arm, mirror and filter mountings (all now with a light green patina), bright lacquered telescopes and fittings (the lacquer finish is pitted to varying degrees, except in the case of the long telescope in which the finish is entirely missing), and a polished rosewood handle. The hand engraved, 7 3/8” radius, inlet silver scale is graduated from -5°—145° by 10’ of arc (figures engraved at 10° graduations and diamonds at 5°). The scale may be read to 10” with the vernier scale (see closeup of vernier scale), clamp & screw fine movement, and swing out magnifier.  The instrument has three horizon glass and four index mirror filters built onto the frame. The long telescope (7 1/4” closed) and short wide field telescopes have complete optics. There is also a short telescope barrel (no optics), a shade tube (eyecup missing?), brass ball tipped adjusting pin, and a folding hand magnifier in a tortoise shell (?) case (Lens badly chipped). There is an empty place in the case for a telescope eyeshade (see image of sextant and accesories in case) . The instrument is engraved english at the far left of the scale arc, and G.E. Butler, San Francisco. (in script-see image of engraving) near the center of the arc (Geo. E. Butler Co. was a nautical instrument dealer in business in S.F. until at least 1984).

The original mahogany case, 10 3/4 x 9 7/8 x 5” is in good condition, with splits at screws/nails at three corners each of the top and bottom panels-see image of case. The case itself is of hand dovetailed frame construction (see closeup image of the dovetails, with layout lines clearly visible), with the top held on with brass wood screws and the bottom held on with steel nails. There is a brass name plate, engraved Stream with many flourishes, set into the top of the lid (see engraved plate). The hook catches for the lid are chemically darkened brass, while the handle is age polished. The key is a replacement. Inside the green felt lining is water damaged, the hinge has a red oxide patina, and the lid has been owner modified (gouged out) to allow the wide field telescope to remain in place on the sextant during storage. There are two trade stickers in the lid of the case, the first under the second (now removed): max kuner co. / nautical instruments / {k-2786|4031}*/ chronometer & watchmakers /804 first avenue / Seattle (click to see image), and Northwest / Instrument Co. /Nautical & Surveying instrument makers / 63 Madison St. { N-9588} Seattle,Wash. (click to see image)

The sextant was owned by Thomas W. Stream (lost at sea in January of 1914), Master of the Edward R. West, an 835 ton Schooner, out of San Francisco CA. (click for image link to U. Wash. Library image)

*Figures enclosed in {} indicate handwritten text.

Sextant Micrometer Detail

icon for detail photo of sextant micrometer

Detail, US Navy micrometer sextant, inscribed "David White Co. Milwaukee, Wis." and "U.S. NAVY, BU. NAV. MARK II (N)* 17424 - 1943" (see closeup of logo) . A similar( but withadjustable polarizing filters) instrument is in the NMAH collection and is described and illustrated at:

These instruments have a cast aluminum alloy frame with the arc graduated on the limb from -5° to 145° (see image of sextant). The micrometer reads to 0.1 minute = 6" of arc. The bronze gear is attached to the limb beneath the arc with screws. The index arm and telescope are of aluminum with brass furniture and nickel-silver screws etc. The handle is made of mahogany.

The 11.25" square by 5.5" deep box is constructed of 5/16" mahogany (see image of case and image of sextant in case) plywood with dovetailed corners (see detail image of dovetail joints). The 1/4" mahogany plywood top and bottom are attached with screws. There is a metal tag on the front of the case (see image of tag).

* The N is inscribed in a circle.

Octant, c. 1800

octant photo icon

This octant has a radius of 13 3/4 inchs (index arm bearing center to vernier edge), while the greatest dimension of the ebony frame is 15 1/8 inchs. The ivory scale is graduated to 20' and can be read to 1' using the vernier. The scale is marked (between 45°&50°) with the Spencer, Browning & Rust "SBR" logo, showing it was graduated between 1785 and 1840 when this firm was in business.*

I obtained this octant in the Summer of 2012, for use in demonstrations and courses on instrumentation/navigation that I teach, and restored it, including fabricating a variety of missing parts. The photo above is of the restored octant. All bright brass parts/furniture and the "ivory" pencil are replacements fabricated by me. Restored parts were left bright to show as replacements. Additional photos, including some detail shots of the restored instrument are available via the links:

I also made replacements for all mirrors since the original silvering had badly degrade on all of them (the original mirrors are stored with the instrument). All replacement mirrors were cut from a thin glass commercial mirror-tile. The half silvered mirrors were prepared by scraping the backing (including the copper and most of the silver) off the desired clear window area with a razor blade and then dipping in 1 M nitric acid to remove the remaining silver. The resulting mirrors are quite functional for my purposes of demonstration.

Details of other fabrication processes will be posted later, or interested parties can contact me.

* What appears to be a nearly identical instrument but with original parts and micrometer adjustment can be seen at the NMAH (Smithsonian) collection.

"Columbus" solid-disk mariner's astrolabe

icon of labeled "Columbus" astrolabe

Life-size reproduction of a c. 1500 instrument in copper sheet by R. Paselk.

Mariners astrolabe

icon for labeled photo of mariner's astrolabe

Life-size reproduction of a late 16th century instrument fabricated from 1/4" bronze plate by R. Paselk.

Mariner's quadrant

icon for labeled photo of mariner's quadrant

Reproduction in fabricated from 1/8" copper-nickel alloy by R. Paselk.


© R. Paselk 2007

Last modified 27 October 2013