Pinhole Projection www.moonshadowmix.co.za www.eclipseafrica.org Claire Flanagan claireflan55@gmail.com 2016

You need: a light that has a shape e.g. the Sun in eclipse a pinhole – make one in a sheet of paper using a sharp pencil a screen – another sheet of paper

How it Works remember: light travels in straight lines

The Sun is a disk of light for us on Earth

. . . sunlight shines in straight lines, in all directions

. . . sunlight shines in straight lines, in all directions But if we limit the light with a pinhole we see something interesting . . . . . . the shape of the Sun!

paper

hole (any shape)

Sun hole

Sun hole another paper

hole sunlight

hole sunlight limited by hole

hole patch of light same shape as hole

If we make the hole smaller then no matter what the shape of the hole we see the shape of the Sun Watch the green rays from one edge of the Sun and the red rays from the other edge

big hole -> light spreads -> we see shape of hole

smaller hole -> light spreads less

small hole -> light from edge of the Sun is focused -> we see shape of Sun hole image of the Sun

smaller hole = better focus (but less light = dimmer image) image of the Sun

Experiment with different shapes and sizes of holes big square small square small triangle big triangle

small square big square small triangle big triangle

different sizes of holes Experiment with different sizes of holes bigger smaller

bigger smaller better focus brighter

further from the screen? What if the pinhole is further from the screen? pinhole screen

If the screen is further, the image is bigger

The best pinhole projecters are gaps between the leaves of trees

Put a sheet of paper on the ground to see images of the Sun

Taller trees give bigger images of the Sun

Pinhole-projected eclipse under a tree, Cape Town 2009 Photo: Simon Fishley

Write your name in pinholes, and photograph the projection Photo: Astronomical Society of Southern Africa

Make pinhole gaps between your fingers . . . Photo: Windell Oskay from Sunnyvale, CA, USA

. . . and watch the eclipse! Photo: Windell Oskay from Sunnyvale, CA, USA

Next solar eclipses for SA . . . Thu 1 Sep 2016 mid-morning Sun 26 Feb 2017 late afternoon Jhb Cape Town www.moonshadowmix.co.za www.eclipseafrica.org