Glossary · Regulation

Chronometer correction

The signed adjustment applied to an indicated chronometer reading.

Explanation

Under the explicit convention error = indicated minus reference, correction = reference minus indicated. A chronometer fast by 12 seconds therefore needs a correction of minus 12 seconds. Historical documents may use different labels or signs: transcribe their headings and worked examples before converting them. A correction from one observation is not an indefinitely valid certificate of accuracy, and a historical correction does not describe the present condition of a surviving instrument.

Diagram

Schematic: chronometer rate record. Rate schematic: correction applies a known gain or loss; it is not proof that the preserved chronometer currently performs to that rate.

Photographic reference

E. Barthet No. 10 — gimballed box, L2015-3496 — © The Board of Trustees of the Science Museum / Science Museum Group / The Clockmakers’ Museum, CC BY-NC-SA 4.0 as stated by source; commercial-use permission review pending. Official museum or publication source

E. Barthet No. 10 — dial and canister — © The Board of Trustees of the Science Museum / Science Museum Group / The Clockmakers’ Museum, CC BY-NC-SA 4.0 as stated by source; commercial-use permission review pending. Official museum or publication source

E. Barthet No. 10 — exposed movement — © The Board of Trustees of the Science Museum / Science Museum Group / The Clockmakers’ Museum, CC BY-NC-SA 4.0 as stated by source; commercial-use permission review pending. Official museum or publication source

E. Barthet No. 10, L2015-3496: exact chronometer context, not evidence of a recorded rate or a lunar-distance observation.

Cross-references

Nearby regulation terms

Breathing: The concentric expansion and contraction of a hairspring.
Breguet overcoil: A hairspring whose outer turn is raised and curved over the body of the spring.
Breguet spring: A hairspring with a raised outer coil to improve isochronism.
Chronometer rate: The known daily rate of a marine chronometer.
Chronometer rate book: A record of comparisons used to follow a chronometer’s error over time.