The nocturnal is a navigational instrument that was first invented in the 16th Century. By focusing on the stars it can estimate the time to within 10-15 minutes.
The outer edge of the instrument is divided into days and months. When this is set, the user holds it up at arm's length so that the North Star shows through the central brass hole. The long arm is then aligned with the star constellation known as The Great Bear. The inner dial is marked in hours and minutes. The time can then be read from where the arm crosses the inner dial. Nocturnals were often favoured by mariners. Some rural communities continued to use them until the early 19th century to set their town clocks.
Only two wooden nocturnals are known to exist in Ireland. The other is in the National Museum of Ireland, Dublin.
This example was donated to Ballymoney Museum in 1873. It is inscribed 'A.R. Kyle 1781'. This is the original owner's name. The maker's name is unknown. For more information on astronomical and navigational instruments, visit the National Maritime Museum website.