National Astronomical Observatory of Japan

Astronomical Information | 2016 | December

The sky of Tokyo

The sky of Tokyo (8:00 p.m. Mid-December)
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Calendar (December)

7First Quarter Moon
10Saturn at conjunction
11Greatest Eastern Elongation of Mercury
14Full Moon/ Geminid Meteor Shower peaks around 9:00 (The best time to observe is after midnight on the morning of the 14th. On the order of 10 meteors per hour are expected. Because the Moon is very bright, conditions are bad.)
19Mercury at stationary point
21Last Quarter Moon/ Winter solstice (Sun’s ecliptic longitude 270°)
23Emperor’s Birthday [Tennou-Tanjyobi] (national holiday)
29New Moon/ Mercury at inferior conjunction
30Uranus at stationary point

The days for the peak activities of the meteor showers are based on the predictions of IMO (International Meteor Organization).


Mercury is positioned low in the southwestern sky after sunset. It reaches greatest eastern elongation on the 11th, but at 30 minutes after sunset its elevation is less than 10 degrees, making observations difficult. On the 29th Mercury reaches inferior conjunction.
Venus can be seen low in the southwestern sky after sunset. Its elevation increases rapidly at the end of the month. Its brightness is -4.1 magnitude to -4.3 magnitude.
Mars can be seen in the southwestern evening sky moving from the constellation Capricorn to the constellation Aquarius. Its brightness is 0.6 magnitude to 0.9 magnitude.
Located in the constellation Virgo, Jupiter can be seen in the southeastern to southern sky before dawn. Its brightness is -1.8 magnitude to -1.9 magnitude.
Saturn’s apparent location is close to the Sun, making it unsuited for observation. Saturn reaches conjunction on the 10th.

Source: Ephemeris Computation Office, NAOJ

With the “Sky Viewer” you can easily explore the appearance of a typical urban night sky (planets and constellations are visible).The Celestial Phenomena section of the glossary explains the planetary phenomena terms: greatest elongation, opposition, conjunction, stationary, etc.


Planetary Phenomena