As an amateur astronomer, I wished to locate the position of the moon on the night of a newmoon day, where I was staying. I was on an island (on which I happended to land the same day morning), through which equator passes and where no alamnacs nor calendars/news papaers /any kind of references are present.

The question tightened the bolts from all the sides, so it is enough if an approximate location of the moon is known/found during the 12 hours night (6:00 hrs PM - 6:00 hrs AM of the next day). No need of locating it exactly!

Can you help me out please?

  • $\begingroup$ How close is close enough? Does "it is near the sun's position" count as close? $\endgroup$
    – tmpearce
    Commented Jul 17, 2017 at 10:48
  • $\begingroup$ So then, in such a case, the question becomes how to locate sun's position during a 12-hr stretch of night @tmpearce ! +/- 10 degrees angle is fine enough, for discussion(s) sake! $\endgroup$ Commented Jul 17, 2017 at 10:51
  • $\begingroup$ If you can use Sun-dial as "moon-dial" ? And you reverse it, because it will show approximately when Sun should be where. So for moon you just do the same thing. And I think that newmoon will be visible only few hours after Sunset. $\endgroup$
    – Jan Ivan
    Commented Jul 17, 2017 at 12:19
  • $\begingroup$ @JanIvan, well, why should I reverse the sun-dial ? As the sun and moon take the same path in the sky (though at different times) ! $\endgroup$ Commented Jul 17, 2017 at 12:25
  • $\begingroup$ @MeaCulpaNay I think u want me to say that u can't watch it, but u can with proper equipment some time after Sunset. And google translates "Newmoon" as "First quarter of moon", so I'm not sure. $\endgroup$
    – Jan Ivan
    Commented Jul 17, 2017 at 12:37

1 Answer 1


Assuming that the night sky is clear, you could even be an amateur astrologer for the stars to tell you where that new moon is. These three diagrams almost need no further explanation.

Alignment of sun, earth and new moon:

(hermit eclipse | The Science: Lunar Months)

Zodiacal constellations are a clock-face-like celestial calendar:

(EarthSky | What is the zodiac?)

Example for January:

(Click here to keep these diagrams visible.)

Some explanation anyway:

Being an amateur astronomer, you know that a new moon occurs when the moon is very close to being in the direct line between sun and earth. That is why a new moon, like the sun, is never in the night sky.

Now, being an amateur astronomer, or astrologer, you know that the zodiacal constellations — Aquarius, Aries, ..., Virgo — take turns...

...aligning with sun and earth, depending on the time of year. On any day of the year, you also know which constellation, perhaps even which star, is in alignment and opposite the sun as seen from earth.

So, to know where the sun is at any moment, imagine a straight line from that opposing constellation/star to you. Extend this line through you and the earth.

That extended line will point to the sun and thus also to the new moon.

In January, as an example, ...

...Virgo is the constellation opposite the sun form earth's perspective. Extend the line from Virgo to you through the earth and that line will point to the new moon.

Incidentally, you don't even have to know beforehand about constellations or stars if you can see the sun set or rise on the horizon and, at the same time, ...

...if you can see which star is rising or setting on the horizon exactly opposite the sun. That would be the star to follow all night. During most of January it would be in Virgo.

(This solution was posted exactly a day after an absolutely new moon, as in solar eclipse.)

  • $\begingroup$ well, it seems you are a professional astronomer / star gazer too! Anyways, thanks for a detailed explanation. Yes, it answers my query in all aspects, theoretically. So assuming without any kind of aid of instruments, still we can imagine lines connecting celestial objects to locate the objects of interest. $\endgroup$ Commented Aug 23, 2017 at 4:32
  • $\begingroup$ As this solution doesn't use wordplay I'm guessing it isn't the one you're looking for, @Mea Culpa Nay. I couldn't resist posting a straight-faced solution, though, after seeing that this realistic puzzle about indirect information wasn't getting enough attention. $\endgroup$
    – humn
    Commented Aug 23, 2017 at 10:14

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