Nocturnal Dial

This OER was designed by the OU Academy of the Lynx (oulynx.org) in conjunction with the "Galileo's World" (galileo.ou.edu) exhibition at the University of Oklahoma.

This activity is designed to be completed in 5 minutes by a typical visitor to the exhibition. For adaptations to other age levels and pedagogical settings, visit the "Planisphere Educational Cluster" below.

Introductory Nocturnal Dial Activity

The Nocturnal Dial is an instrument designed to help individuals tell time by the stars.

** The only supply necessary to complete this activity is a Nocturnal Dial. We recommend this one, http://www.amazon.com/Nocturnal-Hemispherium-Antique-Scientific-Instument/dp/B00CETQLC6/ref=sr_1_2?ie=UTF8&qid=1446824557&sr=8-2&keywords=Nocturnal+Dial. **

1. Set the date with the Media Nox dial.
2. Sight through the central hole toward Polaris, the North Star.
3. The line from Polaris to the pouring side of the Big Dipper acts like the hand of a clock, moving counterclockwise.
4. Turn the leading edge of the large Horologium Nocturnum dial to align with the pointer stars of the Big Dipper.
5. Read the time off the 24 hour dial where it intersects with the Horologium Nocturnum dial.
6. From April to October add 1 hour to obtain Daylight Savings Time (DST) for Oklahoma and other areas that adopt DST.  Remember that DST is one hour later than the Standard time the nocturnal dial indicates.

Historical Background

Nocturnal dials are star clocks to tell time by the stars. The instrument replica we link to above  replicates an original nocturnal dial created by Girolano della Volpaia in Florence in 1569, held in the Museo Galileo in Florence. It consists of three superimposed brass disks:  an outermost disk of days, divided in 360 degrees, with months and zodiac signs; a middle disk divided into 24 hours with an indicator for “Media Nox”; and a top disk with 24 numbered teeth.

Further OER's on the Nocturnal Dial

Use the following OER's to further explore the Galileo's World exhibition.

• Galileo's World iPad Exhibit Guide, itunes.apple.com/us/book/galileos-world-exhibit-guide/id1032005948?mt=1.
• Galileo's World iTunes U Course, itunesu.itunes.apple.com/enroll/FDS-EYK-MRL.
• Galileo's World website, galileo.ou.edu.

Nocturnal Dial Educational Cluster

We want to create variations on this activity that connect the Nocturnal Dial to a variety of ages. Use the following chart and hyperlinks to find the one to best fit your group.