The Blue Hour is the period of the day before or after sunset when the sky is still blue. Usually it lasts about 30 minutes. Key is to have an even surface (or tripod) to stabilise the camera as exposure times of more than one second are necessary.
Blue Hour at Marina Bay, Singapore
https://www.bluehoursite.com/ is helpful in determining when the Blue Hour happens at your location.
Camera Settings: Aperature priority (A) with f4.5 or higher, ISO 200+, Manual focus (MF) and 2 sec. timer with Anti-Shock activated
Airbus A340 at Kingsford Smith Airport
Australian Magpie
Carnival Spirit at Circular Quay
Saltwater Crocodile
Opera House and Harbour Bridge
… many more to come!