Grazing occultation
Encyclopedia
An occultation
Occultation
An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer. The word is used in astronomy . It can also refer to any situation wherein an object in the foreground blocks from view an object in the background...

 is an astronomical event that occurs when one celestial object is hidden by another celestial object that passes between it and the observer. A grazing occultation is a special type of lunar occultation that occurs within a mile or two of the edge of an occultation's predicted path, referred to as its northern or southern limit. Within that narrow zone, an observer may see the star intermittently disappearing and reappearing as the irregular limb of the moon moves past the star, creating what is known as a grazing occultation. From an observational and scientific standpoint, these "grazes" are the most dynamic and interesting of lunar occultations.

The accurate timing of lunar occultations is performed regularly by (mostly amateur) astronomers. If several observers with telescopes and timing equipment are positioned at intervals within this zone, they can each time the sequence of disappearances and reappearances as seen from their observing location. If the positions of the observing locations are measured, the timings can be analyzed afterwards to obtain a very accurate fix of the position of the Moon relative to the star and to determine the details of the lunar mountains and valleys seen in profile along the moon's edge.

Such observations are useful for refining knowledge of the positions and motions of stars. Also, the star's disappearances or reappearances may occur in steps, indicating a previously undiscovered close double star that cannot be resolved by direct observations.

See also

  • Occultation
    Occultation
    An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer. The word is used in astronomy . It can also refer to any situation wherein an object in the foreground blocks from view an object in the background...

  • Grazing lunar occultation
    Grazing lunar occultation
    A lunar occultation occurs when the Moon, moving along its orbital path, passes in front of a star or other celestial object, as seen by an observer...

  • Transit
    Astronomical transit
    The term transit or astronomical transit has three meanings in astronomy:* A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body, hiding a small part of it, as seen by an observer at some particular vantage point...

     (occultations of planets by other planets)
  • Asteroid occultation

External links

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