National Astronomical Observatory of Japan

The sky of Tokyo, Calendar, Planets (May, 2018)

The sky of Tokyo

The sky of Tokyo (9:00 p.m. Mid-may)
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Calendar (May)

3Constitution Memorial Day [Kenpou-Kinen-bi] (national holiday)
4Greenery Day [Midori-no-hi] (national holiday)
5Children’s Day [Kodomo-no-hi] (national holiday)
6η(Eta) Aquarid Meteor Shower peaks around this time. (The best visibility will be before dawn for the 2~3 days around this date. About 5 meteors per hour are expected. The Moon is bright, so conditions are bad.)
8Last Quarter Moon
9Jupiter at opposition
15New Moon
22First Quarter Moon
29Full Moon

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


Positioned low in the eastern sky just before sunrise, Mercury appears close to the Sun and is not suited for observation.
Venus shines in the lower western sky after sunset. Its brightness is -3.9 magnitude to -4.0 magnitude.
In the beginning of May, Mars is located in the constellation Sagittarius and moves east (direct motion). In the middle of May, it moves to the constellation Capricornus. It rises in the southeastern sky around midnight and can be seen in the southern sky before sunrise. Its brightness is -0.4 magnitude to -1.2 magnitude.
Jupiter moves west (retrograde motion) in the constellation Libra. It reaches opposition on May 9 and is suited for observation. Seen from Tokyo in the middle of the month, it rises before sunset and reaches culmination around midnight. Its brightness is -2.5 magnitude.
Saturn moves west (retrograde motion) in the constellation Sagittarius. It can be seen before sunrise in the southern to southwestern sky. Seen from Tokyo in the end of May, it rises before 9 p.m. Its brightness is 0.4 magnitude to 0.2 magnitude.

Reference: 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.