Singaporeans looking up at the night sky on Friday the 13th in September 2019, while swinging lanterns, sipping tea and chewing on mooncakes, might have come off feeling a little cheated.

This is because the full moon this Mid-Autumn Festival in 2019 is indeed smaller than the full moons in preceding months and years.

And that's because the full moon this year is a "Micromoon" -- and not because of the haze.

What is a Micromoon?

Regardless of time zone, the moon will appear just a bit dimmer than usual, because it will be at apogee.

The moon being at apogee means it is at the farthest distance from Earth.

The moon will then appear about 14 percent smaller and 30 percent dimmer than when it is at its closest point to Earth, which is known as perigee.

The moon at perigee will come off as a "Supermoon".

But this smaller and dimmer moon that shone red or orange at times also brought out the photographers.

https://www.instagram.com/p/B2XMXIMnfVt/

Also known as "Harvest Moon"

The full moon heralded the arrival of a traditional harvest festival celebrated in several Asian countries, including Singapore, Malaysia, China and Vietnam.

The "Micromoon", is therefore, also known as the "Harvest Moon".

According to Farmers’ Almanac, a periodical that provides calendars and full moon dates for North America, this rare occurrence of a "Micromoon" appearing on Friday the 13th will only happen again in August 2049.

The Harvest Moon is expected to appear full until early Sunday morning.

With or without haze.

Background on moon mechanics

The moon's orbit around Earth is elliptical, a.k.a. egg-shaped.

Each month, as the moon -- a natural satellite -- orbits the planet, it passes through one apogee and one perigee.

Top photo via @okazaki_707 & @inmortuis_monstrum