Make A Sundial

This lesson can be greatly modified for your students and allotted time frame. You can design and make the stencils and/or gnomons before your students arrive to decrease the difficult and time requirements.

An example of a laser rastered sundial. It does have more precision than one made using spray paint and template but this took 23 minutes to raster whereas using the stencil takes several minutes and multiple stencils could be made.

A sundial is a device that allows you to tell the solar time based on your location as the sun transitions through the sky. You can think of it as a shadow puppet turned into a clock. It is composed of a base with hour indicators and a gnomon which blocks the sun, casting the shadow on the base.

An image of a sundial being used on the Mars rover can be found here: https://apod.nasa.gov/apod/ap990428.html

A video of Bill Nye explaining sundials can be found here: https://www.youtube.com/watch?v=NWDlZ3j-m9g

A video of Bill Nye explaining why the Mars rover has a sundial can be found here: https://www.youtube.com/watch?v=F-Atrlz-cSI

The Earth is a sphere, which rotates on an axis that is tilted by 23.5 degrees from perpendicular with the plane of orbit around the sun. The “middle” of the Earth is called the equator. A location’s distance from the equation is called its latitude and it is measured in degrees.

This matters for our sundial because the spacing between hours on our base will need to be adjusted to account for the angle we are at. We can use a sundial calculator to determine what angles our indicators should be. A good calculator that can help us create our template can be found here: https://www.blocklayer.com/sundial.aspx

Use the Find Latitude button to drop a pin on your location to find your latitude for the calculator.

If students will be designing their own stencils have them save the base and gnomon images the calculator creates. They can import these into the design software to aide in the creation process.

While the calculator creates a gnomon for us, it is important to know how it does it. It is creating a right triangle that has one leg that is the length of our base and the adjacent angle matches our angle of latitude. If your students are able to calculate the second leg based on those inputs, you can have them create their own gnomon. If they don’t have the required math knowledge you can have them explore a right triangle calculator: https://www.calculator.net/right-triangle-calculator.html

 Design for a stencil.

 Design for a freestanding gnomon. You can also just use a block attached to one or both sides of the gnomon.

Design for a laser rastered sundial. TN=True North (geographic north) and MN=Magnetic North.

The following instructions will help with the creation of a sundial base stencil. This can be created either partially or fully by the instructor ahead of time depending on students’ level and time allotted.

You can import the images created by the calculator and use them as a diagram or you can use the lengths and angles produced by the calculator depending on student ability.

There are a few things to keep in mind when creating a stencil designed to be used multiple times.

• As laser cutters see hairline thickness as a cut we have to create rectangles that have our desired thickness. You want the thickness to be large enough to have paint go through but not so thick that it “bleeds”
• You should be designing this as a one-piece stencil so you will need to ensure pieces are separated when it is cut. All pieces must be linked and the more connections each area has the stronger and longer lasting the stencil will be.
• Font greatly matters when it comes to stencil numbers. It can be a good idea to use Roman numerals as they work well in stencils.
• If you adjust the overall size of the base, you will need to adjust the size of the gnomon by the same ratio.