There will be a total lunar eclipse tomorrow morning, when the Earth casts a shadow onto the Moon.
On the day of the winter solstice, December 21, the full Moon will start to pass through the cone of Earth's shadow at 6.32am.
The partial eclipse begins when the Moon first enters the dark inner, umbral part of the Earth's shadow, and will become a total eclipse at 7.40am.
It will reach its maximum at 8.17am, and end at 8.53am.
From southern parts of the UK, the initial partial phase and the beginning of totality will be visible, but the Moon will be dropping down into the western sky as dawn approaches.
From those locations, when totality begins, the Moon will be very low in the west-north-western sky, close to the horizon and in a rapidly brightening sky.
From locations in Scotland and Northern Ireland, totality will be visible in its entirety, but the Moon will be low down after the time of greatest eclipse.
During totality the Moon tracks through the northern part of the Earth's dark umbral shadow, so the southern half will appear considerably darker than the northern part.
John Mason, from the British Astronomical Association, said: "Observers should go out at about 6.30am when, if the sky is clear, the Moon will be visible in the western sky, and they will be able to watch as more and more of the southern part of the Moon becomes immersed in the Earth's shadow.
"They can continue watching until the eclipse becomes total at 7.40am, and hopefully for a little while after this time, if they have an unobstructed western horizon."
The brightness of the eclipse depends on the conditions in the Earth's upper atmosphere through which all light falling on to the shadowed Moon has to pass.
Dr Mason added: "For observers in the British Isles, the very low elevation of the Moon during the total phase means that it is not possible to predict just how dark the Moon will be when it is eclipsed, or what colour it will appear.
"One will just have to go out and have a look."