A new sundial has been installed in Keswick’s Hope Park.
Built by Robert Foster Sundials, of Telford, it replaces the one which had lost its gnomon — the projecting piece that shows the time by the position of its shadow.
Local resident Leonard Will offered his time and money to acquire the new sundial, proudly displayed by park manager Christine Fawcett (pictured).
Time is marked at 10 and 15-minute intervals, so can be read to the nearest five minutes. It also shows the local solar time, from 5am to 7pm and two simple calculations allow people to convert this to Greenwich Mean Time (GMT).
The new sundial points north to Skiddaw and has Keswick’s motto Montes Unde Auxilium Meum (the mountains from whence cometh mine aid) on it.
The sundial’s pillar has an extract from God’s Garden, by Dorothy Frances Gurney, on it.
To tell the time by using the sundial, 12.4 minutes needs to be added to the time shown, to correct for longtitude.
The longitude of Keswick is 3.1 degrees west of Greenwich and the earth rotates at four minutes per degree (360 degrees in 24 hours).
The sun therefore reaches a given position in the sky 12.4 minutes later at Keswick than at Greenwich meridian. You then need to add or subtract the amount shown on a graph on the sundial graph for whatever date it is.
Solar time is sometimes ahead or behind the average time shown on clocks. A copy of the graph is engraved on the dial.
The graph is called the “equation of time”, where “equation” is in the older sense of “correction” or “adjustment” rather than a statement of equality.
To find summer time when it is in effect, add an hour to GMT.