The Beginner’s Introduction To Solar Astronomy

Most people take it for granted. But if you stop and look around, you will understand.

Dominating our daily sky view, Sun it’s the most important star in our system. It is responsible for Earth’s climate, weather, and sea surface changes. Studies conducted by expert astrophysicists, astronomers, climatologists and meteorologists proved short and long-term global temperature variations.

If we take a quick glimpse at it with our naked eye, nothing particular will catch our attention. But Sun’s external surface offers to the wise astronomer many spectacular activities like solar storms, flares, prominences and sunspots.


Now imagine sitting in your backyard, plain daylight, with your own telescope, gazing at the Sun. What a marvelous and unusual situation, isn’t it? Keep following me and I will explain you how to make it reality.

How To Look At The Sun With a Telescope?

Like many other optical observatory instruments, the telescope is used to magnify far sited objects. The operational principle of a simple telescope is based on light collection. As all of you might know the human eye is restricted to collect a particular amount of light. If you want to go over above that value, consider improving your telescope configuration.

Telescopes are usually used to view stars clusters, the Moon, the five constellations and the nebulae. If you plan to use them in their classic way, you will obtain best results when it’s dark and night. But nowadays, the purpose and use of telescopes has further been extended. They are now being widely used to gaze at the Sun.

It might seems somewhat strange that telescopes, capable of actually collecting more light than the human eye, are being used to look at the Sun. That is because Sun, by its own nature, spreads already a decent enough amount of light and heat. Looking at it with a telescope may seem like a bad idea, or a quick way to make the situation worse. But if you think about it, the Sun is nothing but a star, in fact the brightest one in our system.

Solar Sunspots and Faculae - ©NASA/Goddard/SORCE

Solar Sunspots and Faculae – ©NASA/Goddard/SORCE

Sun is in fact so bright that it can not be seen by naked eye for more than a few seconds. Moreover, it has a very high effective temperature of  5778 K – 5505 °C and 9941 °F – which makes it the most critical of all stars. However, devices and filters have been developed and they can easily be used to experience the Sun in a domestic environment. Such telescope sun filters can be used with many ordinary telescopes and will allow you to look at the Sun in a safe way.

List of Solar Filters For Telescopes

With the increase in demand of ways to look at the Sun, the production of telescope solar filters has also been increased. Nowadays, several types of Sun filters are available. Using safe filters for Sun is a quite crucial and mandatory choice, because telescopes will otherwise concentrate sunlight and put your sight in danger.

As a general rule of thumb all filters that are used at the eyepiece should be avoided,  as they have a tendency to get destroyed by concentrated sunlight. A better solution are the solar filter material sheets, especially designed for telescopes. Such sheets requires to be placed at the telescope’s front end, covering its whole aperture size.

Safe solar filters usually have a glass or Mylar coating. Such filters will easily block 99% of the sunlight and prevent it to enter the telescope.

Filters will make the Sun’s surface visible, but it will appear as a disk of pale yellow and possibly other colors, according to your filter nature and telescope configuration.

With proper solar filters you will be able to look at the sun for hours without any risk of danger or damage.

There are so many solar filters available in today’s market. Selecting and choosing such products can take a significant amount of time. Be sure to check and note your telescope’s aperture size.

Here’s some details about commonly used sun filters and their possible application in solar astronomy:

Welding Glass

Welding glass are the most affordable and lower cost solar filter. They do not have a flat or even surface; hence, they give unsuitable results when used with a telescope. However, we can use a welding glass filter to look at the sun with naked eyes. It will give a greenish but large enough image of the Sun.

Metalized Glass

Metalized glass filters are the best solar filters to be used with telescopes. They are build to be fixed at the telescope’s aperture. Made of a flat and uniformly polished glass, covered with a coating of chromium and nickel. Their coating of nickel/chromium will attenuate the sunlight intensity to about one-thousandth of 1%.

Resulting images will give an orange-yellow color of the sun. The metalized glass filters usually costs no more than $200.

Mylar Sun Filters

Mylar is a cheap material and this will make Mylar Sun filters available at a lower cost than metalized filters. They can easily be used with many telescopes. This polyethylene layer is first fixed and fitted in a metal cell which has to be mounted later at the telescope aperture.

Such filters will block a considerable amount of solar radiation, giving a bluish image of the Sun.

Baader Planetarium

Baader Planetarium products have been graded as the safest of all Sun filters. Baader Planetarium is the name of a german company that makes a solar film with high power metalized polymer on both sides. Such filters will have a longer life, will be more efficient and more durable.

Results will give a neutral white image of the Sun, which is the color that resemble most its natural one. They are not more costly than a good glass filter.

Other homemade solutions

Yes, it is true. If you search the web for an homemade way to look at the Sun, you will be amazed by the plethora of results. Many homemade filters can be used to look at the Sun through a telescope. At least that’s what people say.

Such filters may include a Compact Disc with a dense coating of aluminum. Or maybe a Floppy Disk – I do not even know where to find them today. Other homemade filters solutions might be a black and white film, a photographic emulsion bearing image, polarizing filters, and so on.

But all of the above are just unsafe filters. Use them at your own risk, period.

Damages To The Eye Without Solar Filters

Undoubtedly, looking at the Sun is something everyone wishes to try, at least once. Particularly, all people of the world becomes curious to experience the most spectacular event related to Sun, the eclipse.

Partial Solar Eclipse of October 23 2014 - via Flickr user Joshua Tree National Park

Partial Solar Eclipse of October 23 2014 – via Flickr user Joshua Tree National Park

Weeks before the solar eclipse, news channels start showing documentaries for safe sighting, but still many people fail to use the appropriate filters for Sun’s viewing.

Using unsafe or inappropriate solar filters may cause severe damage to the eyes, especially when a solar eclipse occurs. Sun radiation consists of ultraviolet light that can damage eyes and skin. When eye’s retina is exposed to severe ultraviolet light, it gets burned. This might lead to blindness or permanent visual loss.

That being said, enjoy the stunning beauty of Sun. But do it in a safe, secured and easy way.

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