Yohkoh Eclipse Page

Yohkoh Eclipse Page

As many as 5 eclipses of the Sun as seen from the Earth can occur in any one year, in some years there are as few as two eclipses. In the past such events have been the subject of myth, folklore and portents of feast or famine, succes or failure. Scientifically, eclipses were used for such diverse investigations as testing Einstein's theory of relativity, studying the "lunar atmosphere" (before the discovery of the solar corona, the bright halo surrounding the lunar disk during an eclipse was thought to be the moon's atmosphere), and measuring the size of the Sun. Nowadays, eclipses are used to study the large extended atmosphere emanating from the Sun, the corona. The blocking out of the solar disk by the moon means that the faint outer atmosphere can be easily seen. Typically, this outer atmosphere is rich in structure with many helmet streamers being visible. Much of this research into the outer solar corona is carried out using a "phony eclipse" produced by an instrument called a coronagraph which uses a thin metallic disk to block out the Sun's disk. However, nothing beats the eeriness of the daytime sky turning black as the moon moves in front of the Sun.

The most spectacular of solar eclipses is when conditions are just right so that the apparent size of the moon is identical to that of the Sun and when the alignment is just right. In this case, the solar disk is completely covered by the lunar disk and we have a total eclipse of the Sun. If we are lucky, there is at least one total eclipse per year. Unfortunately, the next total eclipse of the Sun visible from the Earth isn't until August 1999. However, the latest occurred across the Caribbean on 26 February 1998. Other parts of the Americas witnessed a less spectacular but still exciting partial eclipse (see below for details). Solar eclipses can also be observed from space and the Yohkoh satellite is in a prime position to catch them. Unfortunately, because of the Yohkoh's orbit, it seldom sees a total eclipse but makes up for it by seeing as many as three partial eclipses for every eclipse seen on the Earth. (Why would a spacecraft see more eclipses than an earthbound observer?).

The Yohkoh science team busily plans for each eclipse. As you can imagine, observing eclipses from space requires a little more planning than observing from the ground. The pages listed below will, hopefully, give you an idea of what is involved! We often use the worldwide web to help us in our planning, because it allows us to communicate efficiently, through recent images and text, with colleagues around the world. Our planning notes from the February 1998 eclipse are also included below, exactly as they appeared on the web.

Path of February 98 eclipse (from NASA)

Planning notes for Yohkoh eclipse observations on 26 February 1998

Learn how we make a Yohkoh movie of an eclipse

Movie from a previous Yohkoh observed eclipse, that of 24 October 1995.

The Yohkoh Solar Eclipse of 26-February-98