I've just got the light pollution overlay to work with the current Google Earth.
Download the Australia overlay from
https://mywebspace.wisc.edu/dlorenz/...ronomy/lp2006/ which seems to be the latest available.
Fire up Google Earth.
"Add"->"Image Overlay"
Give the overlay a name, and use the "Browse" button to link to the image.
In the "Location" tab
1st corner long 94 lat -48
2nd corner long 180 lat -48
3rd corner long 180 lat 8
4th corner long 94 lat 8
Adjust the "Transparency" to suit. About 25% seems to work for me.