This page describes the mechanism of solar eclipses and how to observe it safely. 本頁簡單介紹日食的成因和怎樣能夠安全地觀賞日食。
|Solar eclipse basic knowledge 日食基礎知識|
A solar eclipse occurs when the Moon passes between the Sun and the Earth so that the Sun is wholly or partially obscured. This can only happen during a new moon, when the Sun and Moon are in conjunction as seen from the Earth. At least two and up to five solar eclipses occur each year on Earth, with between zero and two of them being total eclipses. Total solar eclipses are nevertheless rare at any location because during each eclipse totality exists only along a narrow corridor in the relatively tiny area of the Moon's umbra.
There are four types of solar eclipses:
English version: for the geometry involved and activities during solar eclipse, please read the Wikipedia article.
|Observing solar eclipses safely 如何安全觀看日食|
Looking directly at the photosphere of the Sun (the bright disk of the Sun itself), even for just a few seconds, can cause permanent damage to the retina of the eye, because of the intense visible and invisible radiation that the photosphere emits. This damage can result in permanent impairment of vision, up to and including blindness. The retina has no sensitivity to pain, and the effects of retinal damage may not appear for hours, so there is no warning that injury is occurring. Sunglasses are not safe, since they do not block the harmful and invisible infrared radiation which causes retinal damage. Only properly designed and certified solar filters should ever be used for direct viewing of the Sun's disk.
The safest way to view the Sun's disk is by indirect projection. This can be done by projecting an image of the disk onto a white piece of paper or card using a pair of binoculars (with one of the lenses covered), a telescope, or another piece of cardboard with a small hole in it (about 1 mm diameter), often called a pinhole camera. The projected image of the Sun can then be safely viewed; this technique can be used to observe sunspots, as well as eclipses. However, care must be taken to ensure that no one looks through the projector (telescope, pinhole, etc.) directly.
Eclipse glasses 觀看日食專用眼鏡
It is safe to observe the total phase of a solar eclipse directly with the unaided eye, binoculars or a telescope, when the Sun's photosphere is completely covered by the Moon; indeed, this is a very spectacular and beautiful sight, and it is too dim to be seen through filters. The Sun's faint corona will be visible, and even the chromosphere, solar prominences, and possibly even a solar flare may be seen. However, it is important to stop directly viewing the Sun promptly at the end of totality. The exact time and duration of totality for the location from which the eclipse is being observed should be determined from a reliable source.
More info 更多資料:
Last Accessed 最近訪問日期: Wed Jan 29 2020 23:41:22 HKT
Last Modified 最近修訂日期: Wed Mar 09 2016