National Astronomical Observatory of Japan



The sky of Tokyo, Calendar, Planets (August, 2017)

The sky of Tokyo

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

3Uranus at stationary point
8Partial Lunar Eclipse Reference: Local Prediction of Lunar Eclipse / Full Moon
11Mountain Day [Yama-no-hi](national holiday)
12Mercury at stationary point
13The Perseid Meteor Shower peaks around 4:00(The best time for viewing is before dawn on the 13th. On the order of 35 meteors per hour are expected. The Moon is bright, so conditions are bad.)
15Last Quarter Moon
22Total solar eclipse (not visible from Japan)  Reference: Local Prediction of the Solar Eclipse / New Moon
26Saturn at stationary point
27Mercury at inferior conjunction
28Traditional tanabata (traditional star festival)
29First Quarter Moon

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 western sky just after sunset. Its apparent location is close to the Sun making it unsuited for observation. Mercury reaches inferior conjunction on the 27th, after that it can be seen low in the eastern sky just before sunrise.
Venus shines brightly low in the eastern sky before sunrise. Its brightness is -4.0 magnitude.
Located in the constellation Cancer at the beginning of the month, Mars moves east. In the middle of the month it moves into the constellation Leo. Mars is positioned low in the eastern sky before sunrise, but its apparent location is close to the Sun making it unsuited for observation.
Jupiter can be seen in the southwestern to western sky after sunset. At the end of the month, it sets after 20:00 as seen from Tokyo. Its brightness is -1.9 to -1.7 magnitude.
Located in the constellation Ophiuchus, Saturn can be seen in the southern sky after sunset. As seen from Tokyo, it sets after midnight at the beginning of the month and before midnight at the end of the month. Saturn reaches its stationary point on the 26th. Before that it moves slowly to the west (retrograde motion), and after passing the stationary point it moves to the east (direct motion). At the stationary point, it seems to stop with respect to the stars. Its brightness is 0.3 to 0.4 magnitude.

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.