Rare Super Blue Moon to Light Up UK Skies – How and When to See It. The upcoming Super Blue Moon will appear bigger and brighter than usual in the UK skies. The full moon will be visible on Monday, August 19, just before 7.30pm. This event occurs when a full moon coincides with the moon’s closest approach to Earth, making it appear larger and brighter. The term “supermoon” is popularly used to describe this impressive event. Although the moon won’t actually look blue, it may have a reddish tint. Super Blue Moons happen about once every 2 to 3 years.