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Warning: Do not look directly at the Sun with the naked eye or any unfiltered optical instruments
When the short summer nights and long sunny days come around, there's no need to fret about what to see — the daytime has its own highlight.
Stars are fascinating things: at the simplest level they make the patterns of the constellations. Some brighter examples give hints of color, like red Betelgeuse in Orion. The trouble is, every night-time example is so incredibly far away. Fortunately, the Sun is one star that's right on our doorstep and it's available for everyone to look at, understand and, depending on how you're looking at it, gasp in amazement.
The Sun, our source of natural light and warmth, and the star that made life possible on our planet, is just next door in astronomical terms. On average, it's only 150 million kilometers away.
However, the Sun's close proximity makes it brighter and hotter than any other star in the sky. Never look at the Sun using just your eyes, unfiltered binoculars or telescopes — you risk permanent damage to your eyesight. There are a number of options to view the Sun safely.
If you have a refracting telescope, try the projection method. Line the telescope up with the Sun (remembering not to look at the Sun through the telescope) and then hold up a piece of card close to the eyepiece so that an image of the Sun falls onto it.
When projecting the Sun, you'll be able to see that its disc appears slightly darker around the edges than it is in the middle, an effect known as limb-darkening. You'll also be able to see sunspots — providing there are any around. Project the Sun over a few days and you might see the sunspots move and change shape because the Sun rotates quite slowly.
If you want to move on from projecting, you can buy filters that fit over the big, front lens of your telescope. These objective lens filters allow you to look directly through the telescope at the Sun. Because it's quite risky to point your scope at the Sun, these filters must fit properly and must not be damaged in any way. Before you go out to observe the Sun, be sure to seek expert advice from a reputable astronomy shop.
Solar filters block out what you don't want to reach your eye: the Sun's infrared heat, its ultraviolet radiation and 99.9 per cent of its light. What you get is a greatly dimmed, safe image of the Sun. You'll be able to see sunspots and those dark solar edges through the scope and, depending on what kind of filter you buy, the Sun will be displayed in a different color. The cheaper 'white-light' filters are made of black polymer film (aluminum plastic sheet), which gives the Sun a blue tinge, while more expensive glass white-light filters give a more natural orange-yellow look to the Sun's disc.
Then there are the costly hydrogen-alpha (H-alpha) and calcium-K (CaK) filters and dedicated telescopes. These filter all the light and heat coming from the Sun except in wavelengths of hydrogen-alpha or calcium.
At the H-alpha wavelengths, you'll get orange views of the features in part of the Sun's atmosphere called the chromosphere, where dramatic solar flares and outbursts called prominences take place.
Looking through a CaK filter allows you to see magnetic storms that occur lower in the chromosphere, all in a fetching purple. So although these are two expensive options, they certainly produce the 'wow' factor when looking at the Sun.
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All you need is a piece of white card, onto which you project the image of the Sun from your scope or binoculars. You could also fix another piece around the front end of the scope to create a shadow around the projection. Good for eclipses and sunspots.
Cardboard Sun Projector
These kits are simply a small telescope and mirror that projects an image of the Sun onto a white screen on the inside of the box. It will show much the same views as the solar projection setup — great if you don't have a scope.
These glass or film coverings fit completely over the light gathering front end of the scope, stopping all heat and virtually all light from the Sun entering the scope. Good for viewing sunspots and granulation.
Personal Solar Telescope
The Personal Solar Telescope (PST) is made to reveal one specific wavelength of light and can show much more than your naked eye will see with film or glass filters. Good for prominences, active regions, filaments and faculae.
The amazing sight of the Sun's outer atmosphere, the corona, only becomes visible to us on Earth at totality — the height of a total solar eclipse. Of course, the corona is always there, it is simply that its delicate pearly-white structure is usually drowned out by the brightness of the Sun and our daytime sky. Views of the corona can also change quite dramatically depending on how active the Sun is; its shape is influenced by the vast solar magnetic fields. During totality, it is the corona that defines the eclipse for many people, and it is only during this darkest part of a solar eclipse that you don't need special equipment or eye protection to marvel at it.
Sights on the Sun
You'll need a filter to view the sun safely and see the incredible activity on our nearest star. Here's what to look out for:
These features usually appear in pairs and are caused by magnetism, which draws away energy. Their resulting lower temperature makes these regions appear dark.
The photosphere is translucent, so when you look at its center you're peering deep into the hotter, brighter part. This is why it appears lighter than it does at the edges.
The light from the Sun is given off here. Its temperature is around 6,000°C and it is home to sunspots.
These are concentrations of gas, associated with sunspots, that move up from the chromosphere. In just an hour, active prominences can shoot to heights of 750,000km.
A filament is the same as a prominence, except that whereas prominences are seen outside the Sun's disc, filaments are seen against the disc — which makes them a little harder to pick out. Best seen with a PST.
Latin for little torches, these bright patches of the photosphere are found where sunspots have been or are going to appear.
Flares are the most explosive features on the Sun and are associated with sunspots. They are believed to be caused by sudden changes in the Sun's magnetic field. They are best seen with a PST.
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