This year's largest full moon -- the biggest and brightest in six years -- is to appear tomorrow, the Taipei Astronomical Museum said.

In a statement yesterday, the museum said that when a full moon occurs near the moon's closest point to Earth, known as its perigee, it is called a "perigee full moon," or more commonly, a "supermoon."

The full moons both this month and next month are to qualify as supermoons, the museum said.

Tomorrow, the full moon is to reach its peak at 9:19pm, about nine hours after reaching its perigee at a distance of 356,978km from Earth.

It is to appear about one-sixth larger and one-third brighter than April's smallest full moon, with an apparent diameter of 0.57 degrees -- the largest since February 2019 -- the museum said.

The moon typically measures a half a degree in the sky.

To mark the occasion, the museum is to host a super full moon observation event from 7pm to 8pm in front of the Sun Yat-sen Memorial Hall, where telescopes and guided sessions would be provided for the public to enjoy the view.

While the size difference between the largest and smallest full moons is similar to that between the NT$50 and NT$10 coins, the so-called "moon illusion" that is to occur tomorrow would make it seem especially spectacular, the museum said.

A moon illusion is when the moon appears larger near the horizon than it does higher up in the sky.