Apart from a Solar Eclipse, How much time is needed until a Waxing Crescent Moon be seen following a New Moon?

  1. Would the time of year be significant? The Vernal Equinox + 1 Month.
  2. Could it be seen the same night that it occurs?
  3. Could it be seen in the day when it occurs?
  4. Would this be affected if the viewer was in a rural location, without lights? Or would city lights help?


Ancient Lunar calendars depended on observation of the New Moon, (like political / religious obligations).

What was the potential margin of error? Hours? a Day? (Not considering bad-weather.)

From Wikipedia - A New Moon Cannot be Seen:

In astronomy, new moon is the first phase of the Moon, when it orbits as seen from the Earth, the moment when the Moon and the Sun have the same ecliptical longitude. The Moon is not visible at this time except when it is seen in silhouette during a solar eclipse when it is illuminated by earthshine.



1 Answer 1


From the US Naval Observatory: Crescent Moon Visibility:

Naked-eye sightings as early as 15.5 hours after New Moon have been reliably reported while observers with telescopes have made reliable reports as early as 12.1 hours after New Moon.

USNO is usually a very reliable site for info like this.

  • $\begingroup$ - Wayfaring Stranger - That is a incredible answer, and the reference is impeccable. Thank you very much! $\endgroup$ Mar 22, 2016 at 2:45
  • $\begingroup$ I could've sworn someone's asked this here before: it's of fair importance to the Muslim calendar whose month starts with the first visibility of the New Moon. $\endgroup$
    – user21
    Mar 22, 2016 at 14:16
  • 1
    $\begingroup$ @barrycarter This is probably the last astronomy related forum upon which this question has not been asked. $\endgroup$ Mar 24, 2016 at 1:14

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