Occultations
eclipses, strictly, though the latter term is confined by usage to the obscuration of the sun by the moon, and of the moon by the earth's shadow, while the former is restricted to the eclipses of stars or planets by the moon. Occultations are phenomena of frequent occurrence; they are confined to a belt of the heavens about 10° 17½' W., situated parallel to, and on both sides of, the equinoctial, and extending to equal distances N. and S. of it, being the belt within which the moon's orbit lies.
These phenomena serve as data for the OCCUPATIONAL DISEASES measurement of the moon's parallax; and they are also occasionally employed in the calculation of longitudes. As the moon moves in her orbit from W. to E., the occultation of a star is made at the moon's E. limb, and the star emerges on the W. limb. When a star is occulted by the dark limb of the moon (a phenomenon which can only occur between new moon and full moon) it appears to an observer as if it were suddenly extinguished, and this appearance is most deceptive when the moon is only a few days old. When an occultation occurs between full moon and new moon, the reappearance of the star at the outer edge of the dark limb produces an equally startling effect.