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 they would 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 of the 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.