Bearer of bad news?: Eyes on sky as Devil's Comet returns after 71 years

What those with an eye for the sky might find is the Devil's Comet, also known as Pons-Brooks and once known as the bearer of bad news.

Resident astronomer Michael Maher had the first good sighting of the Devil's Comet at The Rock Observatory on Saturday.

It is a sight he said skygazers would find interesting and one you would only see once in a lifetime.

"This one was called the Devil's Comet only because it has an activity which causes it to have two tails at a certain time and someone thought it looked like the horns of devil," Mr Maher said.

"Comets are very mysterious things and up until recently - the last 150 years - people didn't know what they were.

"Up until then comets were always considered holders of bad news."

Mr Maher said people would seek advice from their resident astronomer, usually belonging to the King or landlord, about what the bad news was when a comet would appear.

Often it was thought a comet was linked to a death about to take place.

However, Mr Maher said the lack of knowledge about what a comet was caused fear, which led people to form panicked theories.

"Throughout history there has been a lot of things happen, the Bayeux Tapestry was how this comet was seen in that tapestry during the time the conqueror took over England which people look at as proof," Mr Maher said.

Although it is a fun theory to explore for some, Mr Maher said comets were merely dirty snowballs stuck in space.

"They're just frozen gas with rocks in them and gravel," he said.

"Because they're frozen gas, as they come in closer to the sun, the solar radiation heats them up and effectively vaporises the ice and releases it into the atmosphere and that streams out behind them.

"The tail always faces the sun, so they look like coming in but on the way out they look like they're going backwards."

Over the next few weeks people will be able to catch a glimpse of the comet, which has been described as a beautiful sight.

"In a few weeks it will probably be the best when the moon is gone and it will come up in the west and we can get a really good look at it, which will be interesting," Mr Maher said.

"It probably has another month."

Mr Maher said over time comets would slowly evaporate away, but that could be a billion-year process.

"We encourage people to come out to the observatory and we will show them where to look," he said.