Creative Astronomy - The Ecliptic and Solargraphs
Updated: Aug 2, 2021
Long exposure pinhole camera image of the passage of the sun over Mt Manaia, Whangārei Heads.
I ran a workshop in which we constructed a simple model of the cosmos to look at the movement of celestial objects through the sky. It is a simplified form of an ancient device called an armillary sphere.
The earth is positioned at the centre, orientated with Aotearoa, New Zealand sitting on top. A horizontal disk represents the horizon with Mt Manaia sitting to the north to give us local context. The stars and planets are positioned on an imaginary sphere, just as they appear to us in the sky. A pivoting ring shows how the sun, moon and planets travel through the sky and can be used to demonstrate the rising and setting of the sun, moon and stars.
Once we could predict how the sun travels through the sky, we constructed long exposure pin-hole cameras called solargraphs. The images capture the path of the sun each day over the course of the festival.
How it went:
The iconic Mt Manaia skyline
We set up the armillary sphere at night oriented in front of Manaia. People found the experience of being under the actual sky at the same time as using the sphere really engaging, making connections they hadn’t understood before.
Photo of Armillary Sphere: Ian Piddington Photography
We started on the 1st of January, not long after the summer solstice and just two days after the full moon. This made it easy to position the sun and moon on the ecliptic ring. As the sun set in the west we were able to turn the ecliptic ring and show the sun setting on the model. We could then predict the moon rising in the east shortly after and then watch it for real! Another discovery was that the full moon swept low in the sky, passing just over Mt Manaia but the sun passed high, almost overhead in the middle of the day.
Photo of me with Armillary Sphere: Ian Piddington Photography
Photo taken at night at a later date to give a better view, again at full moon. You can see how the sun and moon are opposite each other on the ecliptic ring and how the moon lines up with the real moon in the sky.
Then we went on to make and install pin holes cameras. These consist of black and white photographic paper positioned inside a drink can with a pinhole in it - it’s as simple as that! They were positioned creatively around the school grounds, many trying to capture the iconic maunga of Manaia with the arc of the sun above. They were left out for 4 days.
The Results were amazing!
The armillary sphere proved to be a really useful tactile device for exploring and learning about the movement of the sun and moon. Going on to use this knowledge creatively to produce an image of the sun’s path engaged people deeply and made them more aware of their environment and what is going on in the sky.