By looking at the Sun, our nearest star, you can see amazing processes going on all the time, but remember, you need to be very, very careful…
The Sun is incredibly bright and can easily damage a human eye if you look directly at it and will certainly destroy eyesight if concentrated through binoculars, telescope or even a camera lens even for an instant. Only use proper solar filters to view the Sun and then only in strict accordance with the manufacturer’s instructions.
It’s sometimes hard to remember that when you see all those tiny twinkling points of light up in the night sky, that each one of them is a raging nuclear inferno. To appreciate this for yourself, you only need look at the Sun. Of course it’s so powerful, you need to take great care as it is very easy to blind yourself. If you are in the slightest bit doubtful about what you are doing, then don’t do it. But if you are careful and follow the guidelines given here, you will find that observing the Sun is both fun and an endless source of fascination.
The Sun is constantly changing and darker areas called ‘sunspots’ move across its disc over the course of a few days. They come and go in a cycle of roughly 11 years. Very occasionally you might see a brighter region on the disc. These are known as ‘faculae’ and are associated with flares where the Sun blows out very hot material into space.
The safest way to see the surface of the Sun or the ‘photosphere’, to give it its correct name, is to project the disc using a small telescope and two cardboard squares. The first square fitted around the telescope tube casts a shadow on the second so you can see the projected disc of the Sun clearly. You point the scope at the Sun by watching the shadow cast by the ’scope; when the shadow is smallest is when the telescope should be pointing in the right direction. Never attempt to look through the telescope! Focus the telescope in the usual way to get a sharp image of any sunspots. The best time to view the Sun is early to mid-morning or late afternoon. The heat of midday can spoil the view, making the atmosphere turbulent and causing images to wobble.
You can get special solar filters to use with your telescope, but only buy these from reputable dealers. These fit over the front aperture of your telescope and are made from either specially coated glass or from a special metallised film called ‘astro-solar film’. This looks a little like aluminium foil, but is designed to block out dangerous radiation such as ultraviolet. Always check such filters before each and every use. Hold them up to a light bulb and check for any scuffs or pinholes which could let sunlight through. If these are present, discard the filter. If you find your telescope supplied with a small filter which is supposed to fit on to the eyepiece, do not use it! These are very dangerous as they can shatter in the heat thereby exposing your eye to the full force of the Sun’s energy.
There is a new type of filter available now called a ‘hydrogen-alpha filter’ often coming fitted into special telescopes designed for solar viewing. These are amazing instruments which will show you otherwise impossible to see features. With such a telescope or filter you can see ‘prominences’, huge fountains of material standing out from the surface of the Sun and also ‘filaments’, which look like dark lines etched on the disc. These are in fact prominences seen from above. The disc of the Sun looks mottled through this type of filter as well. Here you are looking at ‘cells’ of material thousands of miles across, bubbling up from the lower layers of our star.
All in all, the Sun is an amazing, dynamic object and well worth your time as long as you’re careful. After all, it’s astronomy in the warm!