If you have downloaded and installed the free Google Earth application, you can overlay a light pollution map straight into it as follows:

• Locate the light pollution map image you want to overlay. This page has light pollution maps covering the whole world (this one is hard to overlay) and for regions (like Australia). I overlaid the Oceania Map which is a small download of 1.2Mb that extracts into a 280Mb TIFF. You can use the lot, or maybe cut out a smaller section and save it as a .jpg file.
• Open Google Earth and move the Google Earth map over Australia/New Zealand, or whichever area is relevant for the overlay map you are pasting.
• Click 'Add > Image overlay'.
• In name field write 'Light Pollution' (or something suitable), and click browse at the end of the 'Link' field. Browse to the .jpg file of the light pollution that you saved. Move the 'Transparency' Bar to halfway between clear and opaque.
• To line up the picture, you can move the overlay by dragging it in the centre green box on your google map. You can adjust the size and line it up properly by dragging the four corners. Adjust it so that it lines up nicely. It should look like this image (Figure 1).

Click to Enlarge Overlaying Light Pollution Map

• Click OK and Voila!  The layer ‘Light Pollution’ appears in the ‘Places’ listing on the left and can be ‘ticked’ on or off.

Figures 2 and 3 are typical views (Melbourne and Sydney areas) when using Google Earth with the ‘Light Pollution’ layer ‘ticked’.

Click to Enlarge Melbourne area		Click to Enlarge Sydney area