To measure the altitude of a heavenly body (sun, star, etc.) in order to determine the latitude and longitude.
Sextant used to measure angles between objects, especially celestial objects in relation to the horizon, in order to determine position at sea. Marins sextants are often larger and more solidly made than those used for land surveys; They also are fitted with shades, for sighting the sun. (Expl glossary) This sextant fitted with battery-powered light over vernier, and locking mechanism on index arm.
Used aboard the RCMP Arctic patrol schooner 'St. Rock' (1928-1950). The St. Roch was the first ship to cross the northwest passage from west to east (1942) and back (1944), and the first ship to circumnavigate North America (1950). It was retired in 1958: In 1962 it was declared a National Historic site. (Ref. 2).
Metal sextant (including brass & silver); Glass optics; Synthetic fittings/ Pt. Wooden case has brass hardware; Some felt pads on interior bracings. 2 paper certificates: 1 housed in lid under synthetic cover with metal frame, glass bottle contains oil; Came with hair (?) brush.
Number of Parts
Dull grey-black finish applied to most surfaces of sextant(.001) and accessories (.002 - .004). silver scale; Off-white fine adjustment dial. Pt. wooden case is stained and varnished; Some green felt liners over supports.
" H. HUGHES & SON LTD. LONDON. " & "25014" incised on scale. Scale face divided 130 to -5, by single increments; fited with vernier & fine adjustment dial. "HUSUN/ TRADE MARK" appears on round plate fixed to index arm. "25014" & broad arrow symbol incised on lens housing. " PAT./ NO./ 472814 " incised on index mirror casing. " PAT. NO. 30340/34 " incised on horizon mirror casing."28" incised on 3 of 4 filter housings; "28 228" incised on underside of sextant, below index mirror mounting./ Pt. box markings: Plate missing from box top exterior./ Paper label on lid reads " The Officer Commanding/ R.C.M. Police/ Marine Division/ Halifax, N.S./ From: R.C.M. Police "St. Roch"/ Shipped via H.M.C.S. "Labrador" "./ Paper label on box front bears handwritten notation, only partially legible: " M.L. 117/ [illegible]ch II/ [illegible]/s. 7105/ 25014 "./ Paper certificate framed on inside of box lid reads " [emblem]/ The National Physical Laboratory/ TEDDINGTON./ THIS IS TO CERTIFY THAT SEXTANT NO. 25014 named/ H. Hughes & Son Ltd, London/ has been examined at this Laboratory and found to accord with such of the/ requirements of the Specification (Admiralty form 575) as are applicable/ and has passed the tests therein described. The corrections to the readings/ of the arc in addition to the index correction are [in chart form]:- "AT 15 30 45 60 75 90 105 120 / CORR. 0'.0 0'.0 +0'.4 +0'.4 +0'.4 +0'.4 +0'.8 +0.8/ 23rd December 1940/ [signature- G. Darwin] DIRECTOR/ REV.:- S.54.236./ (16123) Wt.29336/802 1,000 10/40 A. & E.W. Ltd. Gp.685 "./ Paper card fixed to inside edge of box reads " IMPORTANT./ In order to maintain the accuracy of this Sextant, we recommend your attention to the following:-/ 1. Keep the working parts regularly lubricated with the/ special oil provided. This should be sparingly applied/ to the underside of the large micrometer pivot screw,/ the micrometer screw bearing and also to the rubbing/ surfaces of the arc./ 2. The arc and micrometer teeth must be kept clean in/ order to prevent any stiffness developing in the index/ bar movement./ 3. Do not apply excessive pressure to the mirrors when cleaning them. "
Sextant itself is complete. This boxed instrument is known to be missing one adjustment tool. From CA of 08/21/1995 by Tony Missio: Undetermined