Partial and total eclipses

The sun may be partially or wholly eclipsed. A partial eclipse is caused by the moon passing over part of the face of the sun. The sun’s disc loses its circular from - one part becomes obscured. The obscuration increases for a time and then diminishes until it disappears altogether. A total eclipse takes place when the moon comes between the sun and the earth, and the whole sun becomes slowly darkened and finally disappears for a time. It is observed that solar eclipses always happen at the time of a new moon, when the sun and moon are on the same side of the earth. Astronomers can calculate when the moon will come between the earth and the sun, and so can predict exactly when an eclipse will take place and how long it will last. Eclipses of the sun are of great value to astronomers because when the sun itself is blotted out from sight by the dark mass of the moon, the sun’s corona, invisible to us in full sunlight, becomes visible and can be examined by the telescope, and its composition determined by the spectroscope.