Why does the moon look so big tonight? What the moon illusion means for July’s buck moon

DashaSci/Tech2025-07-128950

One of the lowest-hanging full moons of the year will be visible tonight in the sign of Capricorn as the Mercury Retrograde nears. Here's everything to know about July's buck moon and what it means.

A full moon is one of the lunar phases where the entire visible side of the moon, facing Earth, is illuminated by the sun. It's all about the alignment; Earth's position is between the sun and the moon, causing the entire near side of the moon to reflect the sunlight.

The so-called moon illusion is a visual trick that makes the moon appear larger near the horizon than when it's in the sky. This perception is influenced by surrounding objects such as trees, buildings and mountains, NASA explains.

Full moons happen every 29.5 days and typically once per month. On the rare occasion we get two full moons in the month it's called a blue moon — hence, the saying “once in a blue moon.” The next one will occur on May 31, 2026.

Here's what to know about July's full buck moon, the moon phases and when is the Mercury Retrograde.

When is the next full moon in July 2025?

The buck moon reached peak illumination at 4:37 p.m. on Thursday, July 10, 2025, according to the Almanac.

The moon will still appear full on Friday, July 11.

Click here to see moonrise and moonset times in your area.

What is moon illusion? Why does the moon look so big tonight?

The July full moon will also a perception phenomenon known as the moon illusion. That’s when the moon appears much larger than usual, particularly when it’s close to the horizon.

NASA offers a few explanations, such as atmospheric conditions, lighting and foreground objects distorting scale.

When is Mercury in Retrograde in 2025?

Mercury will be in apparent retrograde motion during July 17 through August 10. This is a period when, from our perspective on Earth, the planet Mercury appears to move backward in the sky - an optical illusion, as it doesn't actually change direction in its orbit.

The planet closest to the sun orbits much faster than Earth ... so when Earth passes Mercury in their respective orbits, it creates the illusion that Mercury is moving backwards. This Retrograde phenomena typically happens three to four times a year.

Mercury is associated with communication, travel and technology and astrologers have long associated these Retrograde periods with increased miscommunications, delays and technological difficulties, according the Almanac.

What are the moon phases for July 2025?

🌓First Quarter: July 2.

🌕Full Moon: July 10.

🌗Last Quarter: July 18.

🌑New Moon: July 24.

Why is the July full moon called the buck moon?

July's full is known as as the buck moon because the antlers of male deer (bucks) are in full-growth mode at this time of year, according to the Almanac. Bucks shed and regrow their antlers every year, with a larger and more impressive rack as they get older.

The buck moon name is derived from Native American traditions, where the full moon names often track or reflect the changes in seasons, natural rhythms of the year or animal behaviors and names them accordingly.