A partial solar eclipse can pose more risk to eyesight than a full one,scientists have warned.
Stargazers may think "they don't need the same protection as theywould do during a total eclipse" and could suffer long-term retinal damage, the College of Optometrists said.
On Monday, just before sunset, the moon will appear to take a chunk out ofthe sun in a phenomenon lasting roughly 40 minutes.
A leading optometry body has offered guidance to people in the UK wanting to watch the lunar event safely.
Do not look directly at the sun even if wearing sunglasses, which do not protect eyes enough.
Watching through telescopes, binoculars and cameras is risky and should be avoided.
TV or webcam broadcasts are a "reliable and safe alternative".
You can watch directly with specially designed solar filter glasses (with an appropriate CE mark)
Use the "pinhole projection method". This involves putting a hole in a piece of cardboard, and holding it up - with your back to the sun - so the sun's image is projected on to another piece of paper or card.
Gloomy skies are set to stop most Britons seeing the partial eclipse.
Only people in south-west England and South Wales are expected to have any chance of witnessing the moment through a break in the cloud.