BC Gnomonics
Activities & Downloads
Sundial Trivia Quiz
Test your gnomonic knowledge with an original quiz based around instrument classification
Print and assemble this lunar volvelle, and turn your sundials into moondials! This downloadable kit includes one two-piece volvelle and accompanying directions.
Note that this volvelle cannot be used with altitude dials.
To use, rotate the arrow index to the hour indicated on the dial by moonlight (12 am is located at the bottom of the scale; 12 pm at the top). Next, read off the true solar time indicated by the current lunar age mark (number of days since the last new moon).
Lunar Volvelle
Equation of Time
Download the official BC Gnomonics equation of time! Intuitive labels allow an easy conversion from local apparent time to mean time.
To go all the way to civil time, add the appropriate longitude correction for your location (see LAT to Civil Time).
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Also available is an alternate design, more in line with the US Naval Observatory's current definition.
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Equatorial Ring Dial
Print and assemble this simple, two piece equatorial ring dial and find true solar time with impressive accuracy! While using sturdier materials such as cardstock results in a higher degree of stability and precision, simple paper offers a functional, if ephemeral dial.
After cutting out the dial, fold out its three components so that they rest perpendicular to each other. Suspending the dial from the latitude of use allows true solar time to be read from the equatorial ring.
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Rotating the dial so that the upper half of the nodus beam falls on the top of the hour scale will result in the most accurate readings.
Regiomontanus Dial
Print and assemble a fully equipped Regiomontanus altitude dial! For a sturdier dial, affix the printed dial to a backing of cardboard or wood.
The only element not provided for is the plumb bob assembly, which can easily be fashioned from a string and paperclip. The plumb's sliding indicator may be a bead, loop of tape, or any other convenient marker.
This dial includes the declinations of four stars, which can be used to find time at night with the help of a stellar volvelle (coming soon).
Astronomical Clock
Use this simulator and create a fully functional replica of Prague's famed astronomical clock, calibrated for any location of your choosing.​
Upon entering your home city or town, the clock will display local apparent time, mean time, and civil time, along with the seasonal and Italian hour for your chosen location (assuming astronomical accuracy is enabled).
