Starrylady * Eclipse Demonstrator

Home Page Observatories Teaching Presentations Research Publications Images Resources Links	*Starrylady Scale Model Eclipse Demonstrator**
	Here are instructions for making an accurate scale model (1:510100) of the Earth and the Moon, which can be used to demonstrate eclipses on a sunny day. Some aspects of construction involve the use of a sharp knife, so children should be appropriately assisted or supervised, depending on their ages. Materials Preparation of parts Assembly and Demonstration Use as a Group Activity Materials Strip of 3mm-thick timber, MDF or heavy cardboard , approximately 2 centimetres wide by 80 centimetres long Polystyrene ball 25 mm in diameter Wooden bead around 7 mm in diameter Toothpick Wood glue Small pieces of cardboard to support the ball and bead Sticky tape Stanley knife 2 x 19 mm fold-back clips 1-metre tape measure or rule Felt-tip marker Timber or MDF is available from a hardware store, foam balls and wooden beads from fabric or craft stores and stiff cardboard (pasteboard) from newsagents or stationers. Back to top Preparation of Parts Using a tape measure or ruler, measure off a 75-cm length on the wooden strip with the marker pen, leaving a few centimetres spare at either end. Cut two cardboard supports, shaped as shown in the images, one about 5 cm long and the other about 3.5 cm long. Make a slit in the polystyrene ball with the Stanley knife. Insert the long cardboard support into the slit in the polystyrene ball. This is your “Earth”. Glue a toothpick into the hole in the small wooden bead and allow the glue to dry. Trim the toothpick with the Stanley knife, leaving about 2 cm length clear of the bead. Tape the bead with toothpick onto the short cardboard support so that the bead sits just at the top of the cardboard. This is your “Moon”. Back to top Assembling and Using the Model Clip the Earth and the Moon onto either end of the wooden strip at the marks you made in Step 1. The model will sit free-standing on the ends of the clips if you want to display it on a shelf. To demonstrate eclipses, take the model outside on a sunny day. By holding it in a suitable position, you can cast the shadow of the Earth-ball on the Moon-bead (total lunar eclipse). By turning it around the other way, you can get the Moon's shadow to show up on the Earth - note that umbral and penumbral shadows are visible (see full-size image). Tip: It is easier to line up the model if you can clearly see all the shadows on a light-coloured concrete path or a smooth wall. Back to top Use as a Group Activity If you wish to conduct a group activity using this model, it is recommended that you: Pre-slit the foam balls Pre-glue the toothpicks to the beads and cut to length Pre-cut the strips of wood from a large sheet of MDF (cheaper) Pre-cut the cardboard supports Hand out copies of this instruction sheet to assist the students in assembling their own models.	Click on thumbnail image to see larger image

Last Updated: 17 February 2009