The Mid-Autumn Festival falls on September 17 (Tuesday) this year. If weather permits, a bright and round "super moon" (Note 1) with Saturn in its close proximity (Note 2) will also be observable with unaided eyes at night during the Mid-Autumn Festival period.
To facilitate moon watching by the public, the times of moonrise, transit, moonset and full moon during the Mid-Autumn Festival period are listed in the table. At transit, the moon passes the local meridian, reaching its highest elevation for the night due south.
| September 16 (Monday) – the eve of the Mid-Autumn Festival | |
| Moonrise | 5.17pm |
| Transit (elevation 54 degrees) | 11.05pm |
| Moonset | 4.57am (next morning) |
| September 17 (Tuesday) – Mid-Autumn Festival | |
| Moonrise | 5.58pm |
| Transit (elevation 61 degrees) | 11.57pm |
| Moonset | 6.02am (next morning) |
| September 18 (Wednesday) – the day following the Mid-Autumn Festival | |
| Full moon (the moon is below the horizon of Hong Kong at this moment) | 10.34am |
| Moonrise | 6.37pm |
| Transit (elevation 69 degrees) | 0.48am (next morning) |
| Moonset | 7.07am (next morning) |
Although the full moon (Note 3) will occur on the morning of the day following the Mid-Autumn Festival, the moon will be near the perigee (the closest point to the Earth) at a distance of around 357 400km on the Festival and the following day. The diameter of the moon as observed through naked eyes from the earth will appear around 7 per cent (Note 4) larger than that seen when the moon is at an average distance from the Earth. While a partial lunar eclipse will be visible from South America, most parts of North America, Europe, Africa and western Asia during the full moon, the phenomenon will not be visible in Hong Kong.
Please refer to the 9-day Weather Forecast issued by the Hong Kong Observatory and the Weather Information for Astronomical Observation webpage for the latest weather conditions and the astronomical observing conditions during the Mid-Autumn Festival period to plan moon-watching activities.
Note 1: "Super moon" is loosely defined as a full moon near the perigee.
Note 2: The Hong Kong Space Museum will organise an online activity on September 14, sharing tips to observe the moon, and introducing the astronomical phenomenon "Saturn-moon Conjunction".
Note 3: At full moon, the moon is completely illuminated as seen from the Earth, with the moon and the sun located on the opposite sides of the Earth.
Note 4: The difference in angular diameter will be around 14 per cent between the visual size of the moon at perigee (the biggest visually) and that at apogee (the smallest visually), where angular diameter is an angular measurement describing how large a distant object appears to an observer through naked eyes. The visual difference is illustrated in the Annex.
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