A Rare Sky Show: July’s Full Moon and the Moon Illusion
Get ready for a spectacular show in the night sky. The July full Moon rises on 10 July, and it’s bringing with it something special — the Moon illusion, a strange optical effect that makes the Moon appear huge when it’s near the horizon.
If you’ve ever glanced at a rising Moon and thought, “Wow, it looks massive tonight,” you’re not alone. This illusion has fascinated skywatchers for centuries. And this week, you can witness it in full force.
When and Where to Watch It
The full Moon rises just after 22:00 BST (21:00 UT) on July 10 and will glide low across the sky. In the UK, it appears only 6° above the southeast horizon by 23:40 BST. Even when it reaches its highest point — around 01:30 BST on July 11 — it sits just 10° above the southern horizon.
For observers in more southern regions of the Northern Hemisphere, the Moon may climb slightly higher. But the key viewing times are still the same: right after moonrise or just before moonset — when the illusion is strongest.
The Moon will finally set around 04:50 BST (03:50 UT) behind the southwest horizon, wrapping up a shallow and dramatic celestial arc.
What Is the Moon Illusion?
So why does the Moon look bigger near the horizon?
The Moon illusion is a psychological phenomenon. When the Moon is low in the sky, our brains compare it to familiar objects like trees, buildings, or the landscape. This makes it appear much larger than when it’s overhead — even though its size and distance haven’t changed.
Try this simple test: hold out your little finger at arm’s length and cover the Moon. Whether it’s high or low, your finger can still block it completely. It’s your brain, not the Moon, playing tricks.
Why This Full Moon Looks So Low
This July full Moon is notably low due to the current lunar geometry.
Every full Moon occurs when the Moon is opposite the Sun. That means if the Sun is high in the sky, the Moon will be low, and vice versa.
Add to that the Moon’s tilted orbit, which sits at a 5° angle to Earth’s orbital path (the ecliptic). Over an 18.6-year cycle, this orbit shifts. Right now, we’re just coming out of a major lunar standstill — a time when the Moon’s range across the sky is at its extreme.
This leads to especially low full Moons in summer and higher ones in winter, depending on your hemisphere. That’s why July’s Moon feels extra low and slow this year — perfect conditions for catching the illusion.
How to Catch the Moon Illusion
Watch around moonrise (10 July) or moonset (early 11 July).
Choose a viewing spot with a clear, unobstructed view of the southeast or southwest horizon.
Keep in mind: haze and humidity can affect visibility, but also enhance the illusion.
For best effect, look for nearby objects — rooftops, trees, or hills — to give your brain something to compare the Moon’s size against.
Final Thought
Whether you’re a stargazer or just someone who enjoys the night sky, this July full Moon is worth stepping outside for. The Moon illusion is one of those cosmic tricks that never gets old.
Stay tuned to Maple Wire for more night sky guides, science updates, and stories that keep you curious.
