The photos were taken after sunset as nightly flyout to feed took place.
The best time to be there is just before sunset. The flyout usually starts around 20 minutes after published time of sunset.
It's a great shame that RBG are going to submit an application to DECC for the colony to be relocated on the basis that they are causing too much damage to the Gardens. It's a very short sighted policy on the part of the Gardens Trust, and it could mean that one of he most magnificant wildlife spectacles in Sydney, and one that is enjoyed by many visitors every year, could soon be a thing of the past.
In general, I only had around 20 minutes every night between the time that the colony started to flyout and the point where it was simply too dark to photograph them accurately. If anyone's interested in the technical side of things, the photos were taken with a Nikon D200 fitted with a Nikkor 70-200/f2.8 AFS VR lens and a Nikon SB800 flash gun with both camera and flash on fully manual modes. Photos were shot in compressed NEF RAW and processed through RawShooter, LightRoom and PhotoShop.
Because of the limited amount of time that I could shoot every evening, I had to go down to RBG 3 or 4 times a week for a month and a half. Some evenings I didn't get a single decent photo. Mostly this was because it was windy down in the Gardens which usually meant that the bats were blown around too much for me to track them accurately. I can't believe that I want to do it all again this year !