A mysterious object with flashing lights spotted hovering over Melbourne's south-east last night was probably more adolescent than alien in origin, according to an expert.

The object with flashing red, green and blue lights was seen over Carnegie for more than an hour from 9pm in the most recent of a series of sightings over the suburb.

Carnegie mum Toni Koromilas told Radio 3AW it was "very weird".

But Perry Vlahos from the Astronomical Society of Victoria said he had tracked down similar lights three weeks ago and it appeared to be a drone or gyrocopter with LED lights attached.

The object was only a couple of hundred metres high and Mr Vlahos said he could hear a whirring noise.

"I'm sure if you stood under it you would hear some teenagers having a laugh at everyone else's expense," he said.

Melbourne gets an average of one UFO sighting a week.

Mr Vlahos said the sightings increase when a bright planet comes into view or during an astronomical event such as Venus sitting low in the west or Jupiter rising in the east.

"Every year there's potential for people to mistakenly refer to these things as UFOs," he said.

Mr Vlahos said camera movement caused by taking handheld footage with a mobile phone increased the likelihood of recording something that appeared to be alien.

So-called UFO sightings could normally be explained if experts knew all the variables.

"If there is intelligent life in the galaxy I don't believe we've been visited by it," Mr Vlahos said.

"But if somebody is going to make an extraordinary claim about that, I'd like to see extraordinary evidence, not just a shaky image on a camera phone."