ECLIPSE OF THE MOON,

Kumara Times, Issue 1163, 21 June 1880, Page 2

ECLIPSE OF THE MOON,

To-morrow night, if the weather permit and the sky be unclouded, the inhabitants of Kuraara and all places in the same hemisphere of the Earth will be able to witness one of those interesting phenomena connected with the physical structure of the Solar System which in the dark ages were ignorantly viewed as indicative of some evil to come or calamity or pestilence to be feared—a total eclipse of the Moon. Even in the present day there are many people who regard the phenomenon of an eclipse with a kind of superstitious dread. When, however, the cause of an eclipse is fully understood, we can only wonder in admiration with what remarkable precision those well skilled in the science of astronomy can predict the occurrence of these phenomena as they do to a second of time, and point to the event as one betokening the most consummate order and precision in the grand laws of attraction and gravitation which the Supreme Being has ordained should govern our solar system. For the benefit of the young and those persona who may not have paid much attention to the subject we purpose explaining as simply as possible what is the cause of an eclipse of the Moon. All opaque or dark bodies cast shadows in directions opposite to the source of light. It follows, therefore, that as the Earth is a big dark bcdy, it must cast an immense shadow far into the regions of apace in a direction opposite to that of the Sun. Now, the Moon, moving in nearly the same plane of the heavens as the Sun appears to do, passes above or below this shadow—which at the Moon’s distance (200,000 miles from the Earth) is nearly three times the diameter of the Moon— l2 or 13 times in the course of the year, and occasionally passes partially or wholly through this shadow. Besides the dark shadow of the Earth where the Sun is totally obscured, there is a lighter shadow all around the darker one equal to the diameter of the umbra or dark shadow : this is called the penumbra (from pene, almost, and umbra, a shadow). And to-morrow night, or rather at an early hour on Wednesday morning, the Moon will pass through both these shadows, and consequently be totally eclipsed. The time of total obscuration of the Moon will be about 37 minutes. There will be another total eclipse of the Moon during the present 3’oar, on 17th December, when the Moon will be totally obscured for one hour and 29 minutes ; but as this will happen at a much more inconvenient hour (3 a.m.) for most persons to witness it, the present opportunity, if the weather permit, should not be lost by those who desire to see this interesting phenomenon. The following is New Zealand mean time at which the several phases will Occur : the moon’s ix. m. First contact with penumbra 10 49 p.m. First contact with shadow... 1145 ~ Beginning of total phase ... 1 2 a.m. Middle of the eclipse ... 1 21 ~ End of total phase... ... 139 ~ Last contact with shadow .... 2 5G „ Last contact with peuuiahfa 3 53 „ The following cle.soi;i|dio:i of the

effects of the Earth's pemimbra and of the refraction of the Earth’s atmosphere on the Moon during a total eelipse, from Lardner’s Handbook of Astronomy, may prove interesting to our readers or intending obstAvers “ Long before the moon entera within the sides of the cone of the shadow it enters the and is partially deprived of the sun’s light, so aS to reader the illumination of its surface sensibly more faint. It might be in': ferred from this, that the obscuration of the moon is so extremely gradual', that it would be impossible to perceive the limitation of the shadow and penumbra. Nevertheless, such is the splendonr of the solar light, that the tbinest crescent of the snu, to which the part of the moon’s surface near the edge of the earth’s shadow is exposed, produces a degree of illumination which contrasts so strongly with the shadow as to render the boundary of the latter so distinct, that the phenomenon presents one of the most striking evidences of the rotundity of the earth, the form of the shadow being accurately that which one globe would project upon another. If the earth was not surrounded with an atmosphere capable of refiaeling the sun’s light, the disk of the moon would be absolutely invisible after entering withiu the edge of the shadow; For the same reason, however, that we continue to see the sun’s disk, and receive its rays after it has really descended below the horizon, an observer placed upon the moon, and therefore the surface of the moon itself, must continue to receive the sun’s rays after the interposition of the edge of the earth’s disk as seen from the moon. This refracted light falling upon the moon after it has entered within the limits of the shadow, produces upon it a peculiar illumination, corresponding in faintness and colour. to the rays thus transmitted through the earth’s atmosphere. When the moon’s limb first enters the shadow, the contrast and glare of the part of the disk still enlightened by the direct rayis of the sun, render the eye insensible to the more feeble illumination produced upon the eclipsed part of the disk by the refracted rays. As, however, the eclipse proceeds, and the magnitude of the part of the disk directly enlightened decreases, the eye, partly relieved from the excessive glare, begins to perceive very faintly the eclipsed limb, which is nevertheless visible from the beginning in a telescope, in which it appears with a dark grey hue. When tile entire disk has passed into the shadow, it becomes distinctly visible, showing a gradation of tints from a bluish or greenish on the outside to a gradually increasing red, which, further in, changes td a colour resembling that of incandescent iron when at a dull red heat. As the lunar disk approaches the centre of the shadow, this red line is spread all over it. Its illumination in this position is sometimes so strong as to throw a sensible shadow, and to render distinctly visible in the telescope the lineaments of light and shadow upon its surface;”