Nocturnal dial

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Nocturnal dial

Nocturnal dials were used to tell the time at night. The user first moved the dial to the correct day and month, then sighted the Pole Star. Time could be calculated by measuring the angle between the Pole Star and one of the stars indicated on the inner dial.

The obverse face displays an inner plate inscribed with the positions of the principal stars (Cancer ye Crab, Perseus his side, Dolphins tail, Brightness of 7 stars etc). Surrounding this, the outer plate shows the days, months and signs of the Zodiac.

On the reverse the hours are shown on an inner plate, the days and months on the outer plate.

The obverse is inscribed 'Moses Bartlett Exon fecit'. Bartlett was buried in the church of St Mary Major in 1709.

Acknowledgments: RAM Museum