The Transit of Mercury is a pretty rare thing. Only 12 times per century does the planet Mercury transition between the Earth and the sun — appearing as a black dot on the surface.
On 9 May 2016, between 12.12pm and 7.42pm, you should be able to see it in London. It won't be fully visible again in the UK until 2039 — and god knows what will have become of us by then.
The good news is that you don't have to be Sir Patrick Moore to get involved — here are the best places in London to catch the action on Monday.
Hampstead Observatory
You can't see the transit with the naked eye because, as you probably know, it's pretty dangerous to be pointing telescopes directly at the sun. Hampstead Observatory will be open for safe transit tracking, as long as the weather's clear enough.
Entry: Free
Hampstead Observatory, Lower Terrace, Hampstead, NW3
Burlington House
The Royal Astronomical Society hosts a transit viewing event in the courtyard of Burlington House, and members of the public are welcome to come and use the special telescopes with solar filters to view it safely. Staff will be on hand from noon-4pm to help you get the best view and answer all manner of astronomical questions. There's even a mini exhibition of Mercury materials in the RAS Library.
Entry: Free
The Royal Astronomical Society, Burlington House, Piccadilly, W1J 0BQ
Royal Observatory Greenwich
Get involved in a whole day of events at Royal Observatory Greenwich. See the transit through the largest-lensed telescope in the UK (turned to the sun for the first time since 1927) or visit the Astronomy Centre and see it from there. Chat with experts about Mercury and try other spectacular space activities.
Entry: Free to Royal Observatory Greenwich. Tickets to view the transit through the Great Equatorial Telescope cost £5. Book here
Royal Observatory Greenwich, Blackheath Avenue, SE10 8XJ
Flamsteed Astrological Society is running events too, and has some useful information about the Transit of Mercury.
Bromley High Street
Orpington Astronomical Society will be taking over Bromley High Street with telescopes from noon-7pm. Anyone will be able to view the transit as part of their Pavement Astronomy outreach. Check the website for exact times before heading out.
Entry: Free
Pavement Astronomy, Bromley High Street, BR1 1JY
At home
If you can't make it out, watch the transit from the BepiColombo Mercury Mission website — they'll be streaming live images during the transit.
