Safe Solar Viewing

Hi there, my name is David Fuller, host of the “Eyes on the Sky” astronomy series. In this video I'm going to talk about both safe, and unsafe ways to view our nearest star, the Sun. Let's start by talking about the safe methods to view the Sun. Probably the most popular way for amateur astronomers is to use a white light solar filter on the front of their telescope. These block 99.9% of the incoming light, so that the rays reaching the eyepiece where you view the image will not damage your eyes. The can be made of glass, or a thin plastic film – but ONLY use the films made specifically for astronomy – more on that later. Filters like this are a great way to view sunspots, and brighter sections on the Sun called “faculae.” Another method is eyepiece projection. It works best with small refractors, otherwise this requires a few precautions: Unless you have a reflector with an aperture stop like this one, then make one, with a diameter of no more than 2 to 3 inches to avoid too much sunlight entering the tube. Avoid solar projection altogether with a compound type telescope, like this. Remember that the incoming light is concentrated as it is focused – much like a magnifying glass does. So only use the simple Huygenian or Ramsden type eyepieces, as the multiple lens eyepieces have cement in them, which can break down from the concentrated sunlight and mess up your eyepieces. Also, because the sun is so bright, it doesn't hurt to use an aperture stop even on a refractor, like this. It's not like you really need to gather more light! You will lose a bit of resolution, but better to be safe. Another way to view the sun is with a pinhole projection method. I won't go into detail on that here, but these are good to use for viewing solar eclipses, though the image they create is small, and can be dim. But it is a safe way to view the Sun particularly for solar eclipses; it's just simple pinhole in something like aluminum foil, and held in front of a white sheet of paper. If you don't have a way to magnify the image, you can still see large sunspots or a solar eclipse by viewing the Sun naked eye – but only with the proper protection. You can take a solar filter, hold it over your eyes first, then look up, like this. Another way is to use solar eclipse viewers, solar eclipse glasses, or even simple sheet of solar film and then look at the Sun. Welders glass can be used too, but NOT anything less than #14 - the #12, #10 and under are NOT safe, and stacking welders glass is not safe either. ONLY use #14, or don't look at all. Here is a list of things that are absolutely NOT SAFE for solar viewing: Sunglasses, Multiple Sunglasses stacked together, Mylar Balloons, Mylar Food Wrappers,  Smoked Glass, X-Ray Film, Film Negatives, CD's or CD-ROM's, Stacked Welder's Glass, Liquid Filters, Coffee, Sun tea, Eclipse Glasses and Telescopes Together or Eyepiece Solar Filters. Some older telescopes came with “eyepiece solar filters” like this one. Do me a favor, if your old telescope came with one of these THROW IT OUT. They are not safe, they have cracked and subsequently allowed unfiltered sunlight to reach eyepieces, and if your eye is there at the time, it can definitely cause blindness. Because solar filters can be expensive, there are ways to MAKE a solar filter – like this one. Baader or Thousand Oaks Optical both sell solar filter film for a reasonable price that can be made into a simple solar filter. I have links on “eyes on the sky dot com” that show you how to make your own filter for less than a retail version. One thing to be careful of is do NOT use “photographic” solar filter film for visual use – it lets in too much light and can damage your eyes. Also, those two companies or any filter by Meade, Celestron or Orion telescope should be just fine. A couple more things to remember: Use common sense – if the filter you are using hurts your eyes, STOP looking – but note that damage may be done to your eyes with unsafe methods that do not cause pain to your eyes too. That is why it is important to ONLY use safe methods. It is not safe to look at the sun even at sunset when it is low on the horizon. Also, be careful when using eyepiece projection methods, as concentrated sunlight is leaving the eyepiece. NEVER put your eye to the eyepiece of a telescope unless it has a VISUAL USE solar filter on the end of the tube, in front of the lens or mirror. Keep your finderscopes capped – on BOTH ends, to avoid possible burns or other injury. Use the shadow of your telescope to aim your telescope at the Sun. And secure visual filters on the front of our telescope with tape or set screws, so they do not accidentally fall off. The Sun can be a fascinating object to view, and can be done safely with the right proetection and a few precautions. For more information, visit eyes on the sky dot com. I'm David Fuller, thanks for watching ,and stay safe.