Sky Diary
Find out what’s up in the night sky:
upcoming astoronomical events, interesting observations, packed with everything a stargazer needs to know
November 2017

*Observations are described for the NORTHERN hemisphere and can be made by naked eye, small binoculars or by small telescope.

Phases of the Moon
Full Moon:November 4
Last Quarter:November 10
New Moon:November 18
First Quarter:November 26

Mercury reaches the greatest eastern elongation (22 degrees from the Sun) on November 24. This means it is east from the Sun and therefore it is observable just after the Sun's setting. However, the ecliptic is low on the western horizon in November, so that Mercury sets already around 4:45 p.m. local time. On November 20, Moon will be about 6 degrees above Mercury.


This planet can be observed in the early morning as a very bright object over the eastern horizon, but its visibility is shorter than it was in October (Venus rises later). Jupiter will be very close to Venus on November 13 morning and this should be a beautiful conjunction (close approach). On November 17 morning this pair will be accompanied by the Moon and this will be another beautiful sight.

Observation of the Moon: Basic orientation

Our Moon is relatively close to our planet Earth and some details on its surface are visible even with a naked eye. When the Moon moves across the sky, you can notice that the boundary between its illuminated and non-illuminated part moves from the right to the left. This boundary is called the TERMINATOR. When the Moon is exactly between the Earth and Sun, we do not see it - we speak about the New Moon. Then, the MORNING terminator starts to move from the right to the left, i.e. the Sun RISES on the Moon's surface exactly on the morning terminator. If you were standing on the Moon's surface exactly on the morning terminator, the Sun would rise for you naturally on your EASTERN horizon (this is the definition of LOCAL EAST on any planet or moon). However, if you stand on the Earth's surface and look towards the Moon, then you see its illuminated part to the right, i.e. to the LOCAL WEST on the Earth. Hence, the right boundary of the Moon is towards Moon's LOCAL EAST, and its left boundary is towards its LOCAL WEST. So, please, remember: local East and West on the Moon are towards Earth's local West and East, respectively, i.e. they are INTERCHANGED with respect to the Earth. There is no problem with the Moon's local North and South, which are towards the top and bottom of the Moon's disk, respectively.

When the morning terminator halves the Moon's disk, we have the First Quarter. Approximately after another 7 days the morning terminator reaches the left boundary of Moon's disk (i.e. the Moon's west) and we have the Full Moon. Then, on the right (locally eastern) Moon's boundary, the EVENING terminator appears and moves again from the right (Moon's east) to the left (Moon's west). If you were standing on the Moon's surface on the evening terminator, you would see the Sun SETTING DOWN on your local western horizon (this is the natural definition of the local west). When the evening terminator halves the Moon's disk, we speak about the Last Quarter. Then, after another 7 days, the evening terminator reaches the left (Moon's western) boundary of the Moon's disk, the Moon is exactly between the Earth and Sun, and we have again the New Moon.

Please notice that the full cycle of the Moon's phases takes about 29 full days (i.e. 29 x 24 hours) as measured on Earth. For a given, fixed place on the Moon, approximately one half of this time (14.5 full days on Earth) the Sun is over the local horizon (= one "day" on the Moon), and another half of this time (14.5 full days on Earth) the Sun is under the local horizon (= one "night" on Moon).

This never-ending play between the darkness and light, the Moon's day and night, is the easiest observation on the Moon that can be made by naked eye.

Article by (C) G. Okša