Sun moths (Castniidae)

Thanks! Very excited to discover it, had a feeling it was there! Now to go back and work out how many!

Sorry Michael, finger slipped.

Yes, see http://lepidoptera.butterflyhouse.com.au/cast/cast-under.html

Does the underwing pattern check out sufficiently well to be sure it's S. plana?

Potentially over 15 individuals outside of the Defence area. This section of grassland has just been fenced off for Lawson Stage 2 where I assume everything will be torn up, I can only hope that there are many residing within the cordoned off area.