Partial solar eclipse

A partial solar eclipseA solar eclipse seen from within the Moon's penumbra. The Moon appears to block part (but not all) of the Sun's photosphere. will occur outside the path of totalityThe path (up to about 270 km wide) that the Moon's shadow traces on the Earth during a total solar eclipse. and within the area swept by the Moon’s penumbraThe part of a shadow (as of the Moon or the Earth) within which the source of light (the Sun) is only partially blocked. Also, the lighter outer area of a sunspot.. During a partial solar eclipseA solar eclipse seen from within the Moon's penumbra. The Moon appears to block part (but not all) of the Sun's photosphere., the Moon appears to gradually cover the Sun, starting with a small bite out of it and progressing to increasing coverage. The proportion of the Sun’s diameter covered (called the magnitude(of a solar eclipse) The fraction of the apparent diameter of the Sun covered by the Moon. By convention it is usually quoted at maximum phase. of the eclipseThe alignment of celestial bodies so that one is obscured, either partially or totally, by the other.) will increase to a maximum and then reduce again as the Moon moves across the Sun. Figure 3-1 shows the progression of a partial solar eclipseA solar eclipse seen from within the Moon's penumbra. The Moon appears to block part (but not all) of the Sun's photosphere. of maximum magnitude(of a solar eclipse) The fraction of the apparent diameter of the Sun covered by the Moon. By convention it is usually quoted at maximum phase. 73%.

The whole event can take up to about three hours. The maximum magnitude of a partial eclipse and the duration of the partial eclipse depend mainly on the distance of the observing location from the path of totality. As examples, for the maximum magnitude of the partial eclipse seen at various locations across Queensland see the map in the article on the 14 November 2012 eclipse  and the map in the article on the annular eclipse of 2013.

During these partial phases, images of the crescentThe phase of the Moon when it appears to be less than half illuminated, or something of similar shape such as the Sun during a partial solar eclipse. shape of the Sun can be seen projected under trees on the ground or onto adjacent walls, as the gaps between leaves act as pinhole projectors. See figure 3-2. Interesting crescentThe phase of the Moon when it appears to be less than half illuminated, or something of similar shape such as the Sun during a partial solar eclipse. shapes can be seen using items with one or more holes in them such as a kitchen colander or a loosely woven straw hat.

Shadows become unnatural as the crescentThe phase of the Moon when it appears to be less than half illuminated, or something of similar shape such as the Sun during a partial solar eclipse. Sun becomes thin, being very sharp in one direction and blurry at right angles. This is easy to see by observing the shadow of both hands with the fingers on one hand orientated at right angles to the fingers on the other hand as demonstrated in figure 3-3.

During a partial solar eclipseA solar eclipse seen from within the Moon's penumbra. The Moon appears to block part (but not all) of the Sun's photosphere. the light level will drop to an extent dependent on the maximum magnitude(of a solar eclipse) The fraction of the apparent diameter of the Sun covered by the Moon. By convention it is usually quoted at maximum phase. of the eclipseThe alignment of celestial bodies so that one is obscured, either partially or totally, by the other.. Because our eyes are very good at compensating for varying light levels, this will often go unnoticed until the Sun is reduced to a very thin crescentThe phase of the Moon when it appears to be less than half illuminated, or something of similar shape such as the Sun during a partial solar eclipse..

How much of the Sun is eclipsed during a partial eclipseThe alignment of celestial bodies so that one is obscured, either partially or totally, by the other. can also be described by the term obscuration(of a solar eclipse) The fraction of the Sun's area covered by the Moon. which is the fraction of the Sun’s area covered by the Moon.

It is not safe to view any part of a partial solar eclipseA solar eclipse seen from within the Moon's penumbra. The Moon appears to block part (but not all) of the Sun's photosphere. without proper eye protection.

Construct and use a pinhole projector or use binocular or telescope projection to see a partial eclipse or use other safe observing methods as described in the article How to Observe the Sun Safely.

Upcoming partial solar eclipses visible from Australia will be on 14 November 2012, 10 May 2013 and 29 April 2014.

Total solar eclipse

A total solar eclipse starts with initial partial phases as described in the article about partial solar eclipses, with the Moon progressively covering the Sun. After about an hour or so, the Moon completely obscures the Sun for a brief period in the total phase of the eclipseThe alignment of celestial bodies so that one is obscured, either partially or totally, by the other.. The Moon then moves progressively off the Sun in the final partial phase, taking a further hour or so. See figure 3-5.

The initial partial phase progresses with very little change being noticeable in the light level. As the total part of the eclipseThe alignment of celestial bodies so that one is obscured, either partially or totally, by the other. approaches, the light level drops conspicuously and an ominous darkening of the sky (the Moon’s shadow) approaches silently from the west. The Sun is reduced to a very thin crescentThe phase of the Moon when it appears to be less than half illuminated, or something of similar shape such as the Sun during a partial solar eclipse.. The temperature can drop and the light quickly begins to fade. By this time animals have become confused at the fading light and often react as if it is nightfall with, for example, birds returning to roost.

For a minute or two before totalityThe period during a solar eclipse when the Sun's photosphere is completely covered by the Moon and the period for a lunar eclipse when the Moon is in the complete shadow of the Earth. begins and for a similar time after it ends, narrow bands of shadow sometimes seem to race across the landscape. These shadow bandsFaint ripples of light sometimes seen on flat, light-coloured surfaces just before and just after totality. occur when regions of the Earth’s upper atmosphere bend the final sliver of light from the thin crescentThe phase of the Moon when it appears to be less than half illuminated, or something of similar shape such as the Sun during a partial solar eclipse. Sun.

 In the final few seconds before totalityThe period during a solar eclipse when the Sun's photosphere is completely covered by the Moon and the period for a lunar eclipse when the Moon is in the complete shadow of the Earth. the last brilliant parts of the Sun’s surface shine through valleys around the edge of the Moon in a shimmering display called Baily’s beads. Finally, the beads are reduced to a single point and the Sun for a few seconds looks like a dazzling diamond ringThe effect seen in the few seconds just before and just after totality of a total solar eclipse when there is a single point of sunlight brilliantly shining through a valley on the limb of the Moon.. The diamond ringThe effect seen in the few seconds just before and just after totality of a total solar eclipse when there is a single point of sunlight brilliantly shining through a valley on the limb of the Moon. and Baily’s beads are clearly defined because of the lack of an atmosphere on the Moon

Figure 3-6 is an image of the Diamond RingThe effect seen in the few seconds just before and just after totality of a total solar eclipse when there is a single point of sunlight brilliantly shining through a valley on the limb of the Moon. at the total solar eclipseA solar eclipse seen from within the Moon's umbra. The Moon appears to completely block the Sun's photosphere. of 2005 in the South Pacific Ocean. The last portion of the Sun is shining through a valley on the edge of the Moon to create one dazzling point, and the coronaThe upper atmosphere of the Sun that appears as a halo around the Sun during a total solar eclipse. becoming visible around the rest of the Sun completes the effect.

As the last bright point winks out, the Sun’s crimson pink upper surface, the chromosphereThe lower atmosphere of the Sun just above the photosphere that appears as a thin crimson ring around the edge of the Sun during a total solar eclipse., can be seen in an arc around the edge of the Moon. Often evident are prominences, bright pink loops of plasma which extend above the chromosphereThe lower atmosphere of the Sun just above the photosphere that appears as a thin crimson ring around the edge of the Sun during a total solar eclipse..

Figure 3-7 is a combination of four images showing the transition at second contactOne of the instances when the apparent position of the edges of the Sun and the Moon (for eclipses) and the Sun and a planet (for transits) cross one another during an eclipse or transit. They are designated as first, second, third and fourth contact. (the start of the total part of the eclipseThe alignment of celestial bodies so that one is obscured, either partially or totally, by the other.) at the total solar eclipseA solar eclipse seen from within the Moon's umbra. The Moon appears to completely block the Sun's photosphere. of 2006 in Egypt. Baily’s beads are visible along with the crimson arc of the chromosphereThe lower atmosphere of the Sun just above the photosphere that appears as a thin crimson ring around the edge of the Sun during a total solar eclipse.. Several prominences are seen rising up from the chromosphereThe lower atmosphere of the Sun just above the photosphere that appears as a thin crimson ring around the edge of the Sun during a total solar eclipse.. As the Moon gradually moves during the sequence, Baily’s beads, the chromosphereThe lower atmosphere of the Sun just above the photosphere that appears as a thin crimson ring around the edge of the Sun during a total solar eclipse. and the prominences are progressively being covered.

As the Sun disappears, the Moon’s shadow arrives, enveloping observers and causing the whole sky to become a dark steel blue, in a surreal twilight almost a million times fainter than the daytime sky, or about the same as night-time with a full moon. During totalityThe period during a solar eclipse when the Sun's photosphere is completely covered by the Moon and the period for a lunar eclipse when the Moon is in the complete shadow of the Earth. when the Sun’s bright surface (photosphereThe bright, visible surface of the Sun.) is completely obscured, the Moon appears as a black hole in the sky outlined by the Sun’s softly glowing pearly white coronaThe upper atmosphere of the Sun that appears as a halo around the Sun during a total solar eclipse., the Sun’s outer atmosphere composed of ionised gas. The coronaThe upper atmosphere of the Sun that appears as a halo around the Sun during a total solar eclipse. curves out from the Sun, usually in a pattern formed by the Sun’s magnetic field. Observers can look for coronal streamers and polar tufts noting the length and distribution of the streamers and features indicating the magnetic field and level of the Sun’s activity.

Figure 3-8 shows the coronaThe upper atmosphere of the Sun that appears as a halo around the Sun during a total solar eclipse. during the eclipseThe alignment of celestial bodies so that one is obscured, either partially or totally, by the other. in July 2010 in French Polynesia. Polar brushes are seen at the top and bottom coming from the Sun’s north and south poles. Several long streamers can be seen in the areas between the poles and the Sun’s magnetic field is apparent. There is a prominenceA large-scale gaseous formation above the surface of the Sun shaped by the Sun’s magnetic field. rising above the Moon on the left hand side of the Sun.

In the darkened sky, planets and bright stars become visible. There is a glowing light around the horizon which has a sunset colour caused by the scattering of different wavelengths of light in the atmosphere (see the explanation in the article on light and colours in the atmosphere).

Figure 3-9 shows the eclipsed Sun in the sky over the Great Wall of China in 2008. The dark area of the Moon’s shadow in the sky can be clearly seen as well as the pinkish sunset glow of the light from outside the shadow over the distant mountains. Planets extend to the upper left of the Sun.

It is the dramatic change from daylight to night, the ominous darkening of the sky approaching silently from the west, the chill in the air and the sudden disappearance of the Sun in an otherwise normal day that so terrorised ancient people. Even today, when we understand what is happening, it is still a spine tingling and awe inspiring event.

At the end of totalityThe period during a solar eclipse when the Sun's photosphere is completely covered by the Moon and the period for a lunar eclipse when the Moon is in the complete shadow of the Earth. the entire sequence is reversed, with prominences, chromosphereThe lower atmosphere of the Sun just above the photosphere that appears as a thin crimson ring around the edge of the Sun during a total solar eclipse., diamond ringThe effect seen in the few seconds just before and just after totality of a total solar eclipse when there is a single point of sunlight brilliantly shining through a valley on the limb of the Moon., Baily’s beads and shadow bandsFaint ripples of light sometimes seen on flat, light-coloured surfaces just before and just after totality. again being visible. The Moon’s shadow races away to the east. The Moon then gradually uncovers the Sun taking another hour or so until the final partial phase is over.

Some people see a partial solar eclipseA solar eclipse seen from within the Moon's penumbra. The Moon appears to block part (but not all) of the Sun's photosphere. and wonder why others talk so much about a total solar eclipseA solar eclipse seen from within the Moon's umbra. The Moon appears to completely block the Sun's photosphere.. There is a dramatic difference between the two.

Because the change in level of brightness from full sun to being in an eclipseThe alignment of celestial bodies so that one is obscured, either partially or totally, by the other. is a factor of almost a million to one, even if you are close to the path of totalityThe path (up to about 270 km wide) that the Moon's shadow traces on the Earth during a total solar eclipse. and the Sun is covered 99%, the light is still up to 10 000 times brighter than in the path of totalityThe path (up to about 270 km wide) that the Moon's shadow traces on the Earth during a total solar eclipse.. It is far too bright to see the coronaThe upper atmosphere of the Sun that appears as a halo around the Sun during a total solar eclipse., the chromosphereThe lower atmosphere of the Sun just above the photosphere that appears as a thin crimson ring around the edge of the Sun during a total solar eclipse. and any prominences and you will not be enveloped by the dark shadow or see Baily’s beads or the diamond ringThe effect seen in the few seconds just before and just after totality of a total solar eclipse when there is a single point of sunlight brilliantly shining through a valley on the limb of the Moon.. Being just outside the path of totalityThe path (up to about 270 km wide) that the Moon's shadow traces on the Earth during a total solar eclipse. is just like almost winning the lottery. There is no prize for a ticket number that is close to the winning one.

Shown on these pages are images illustrating some of the phenomena that can be observed during a total solar eclipseA solar eclipse seen from within the Moon's umbra. The Moon appears to completely block the Sun's photosphere.. Beautiful as the photos are, no image or video screen can make it become a million times darker at midday, arousing some primal emotion. Nor can it effectively capture the beautiful detailed structure in the Sun’s coronaThe upper atmosphere of the Sun that appears as a halo around the Sun during a total solar eclipse., something that only our eyes can see. You have to see and experience a total solar eclipseA solar eclipse seen from within the Moon's umbra. The Moon appears to completely block the Sun's photosphere. outdoors under an open sky to fully appreciate it.

See How to Observe the Sun Safely for safe methods of observing a total solar eclipseA solar eclipse seen from within the Moon's umbra. The Moon appears to completely block the Sun's photosphere..

Annular solar eclipse

An annular solar eclipse occurs when the Moon passes directly in front of the Sun but because the Moon at that time appears to be smaller than the Sun (the Moon is further from the Earth and/or the Earth is closer to the Sun) it cannot completely cover the Sun and a ring or annulus of the Sun remains. Figure 3-10 shows the sequence of the annular eclipse of 2010. An annular eclipse is similar to a partial eclipse, with some of the bright surface of the Sun always being visible. The sky does not become very dark and the dramatic effects of a total eclipse do not occur. The same interesting shadow effects and projected crescent images seen at a partial eclipse can be experienced with the highlight being circular images seen at annularity (when the ring of sunlight is seen around the Moon). For more information see the article about annual solar eclipses for description of the mechanism of an annular eclipse and the article about the annular eclipse of 2013.

See How to Observe the Sun Safely for safe viewing methods of an annual solar eclipseThe passage of the new moon directly between the Sun and the Earth when the Moon's shadow is cast upon the Earth. The Sun appears in the sky either partially or totally covered by the Moon..