# Shortt Free Pendulum Clock Performance

## Raw data (via Woodward via Boucheron)

I have been asked a number of times for data that Pierre Boucheron
collected during his experiment comparing a Shortt free pendulum clock against
a USNO cesium clock reference.
The experiment was devised and measurements made by Pierre Boucheron.
A decade later Philip Woodward digitized the hardcopy and extrapolated missing samples.

The following file contains hourly measurements between SH41 and the USNO cesium clock.
The first column is the sample number.
The second column is the error in seconds (aka phase difference).
The data covers 8464 continuous hours (approximately 352 days, or 50 weeks; almost a full year).

First sample: 1984-10-18 00:15:00 UTC (DOY = 292, Thu, STOD = 900) = JD 2445991.51042 = MJD 45991.010417

Last sample: 1985-10-05 15:15:00 UTC (DOY = 278, Sat, STOD = 54900) = JD 2446344.13542 = MJD 46343.635417

Download: 1984-sh41-hourly-error.dat (122 KB) sh41a.dat

Derived from the above, the following file contains hourly rates (frequency averages, tau=3600 seconds).
8463 data points.
Samples are relative frequency error, adjusted for zero mean rate.
The first two lines are semi-colon prefixed comments.

Download: 1984-sh41-hourly-rate.dat (129 KB)

See also my Shortt papers:
Precision Pendulum Clocks, Gravity and Tides

The following are sample plots made from this data set.

## Spectrum and Progressive Time Error (Woodward)

## Stability Analysis (using Stable32)

## Spectrum (from my BHI 150th paper)

## Stability Analysis (using TimeLab)

## Spectrum (simple sin/cos PSD program)

## Detail from 10 to 28 hours

## Detail of ~12 hour region

## Further zoom of ~12 hour region

## Detail of ~24 hour region

## Detail of ~3 hour region

## Table of tidal periods, via web

## Stability Analysis (using Plotter)

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