Lunar limb

Source: Wikipedia, the free encyclopedia.
Two contrasting lightnesses of the lunar disc at crescent phase, overexposed to show earthshine. Across the Moon, the lunar terminator is visible, the borderline between the Moon's day and night; the lunar limb is the Moon's profile against the dark sky, top right in this picture.

The lunar limb is the edge of the visible surface (disc) of the Moon as viewed from Earth.[1] Seen from afar, it looks like a circular arc, but with higher resolution, we can see that the Moon’s surface is not flat and therefore its profile is irregular.

The lunar limb is not always the same: because of the

collimated rays of sunlight that shine through in some places while not in others during a solar eclipse
.

The contrast of the bright lunar disc against a black night sky makes the lunar limb a popular target when testing telescope optics (including binoculars).

References

  1. ^ "List of basic lunar features". Archived from the original on 2006-02-03.
  2. ^ O'Byrne, Chris. "Lunar Limb Corrections". Archived from the original on 2008-01-13.
  3. .