The Dark Side of the Sun: More on the Great American Eclipse
August 21 is going to be a very exciting day. From coast to coast in the United States, it's solar eclipse day. Regardless of how close to the path of totality you plan to be, you need to be prepared.
Seeing the sun in the sky isn't at all unusual. Except when its cloudy or when you don't go outside at all, you'll probably catch a glimpse of it at some point on most days. But people rarely feel a compulsion to stare at it — it's simply too bright. But when solar eclipse time rolls around, a small percentage of people will suffer vision damage from watching the event. Most problems will probably be temporary, but some may be permanent. And there's no way to know until it's too late. In most cases, the damage won't even be apparent for some hours later. You could believe that everything is fine when the eclipse is over, only to realize later that evening that you can't see as well as you used to. Don't risk this happening to you.
And even if you think you're prepared and have your eclipse glasses and a solar eclipse filter for your camera, you may be in for a surprise. As the date for the eclipse gets closer, there's money to be made by selling eclipse supplies, and not all sellers are fully reputable. Out of a sense of abundant caution, Amazon recently emailed all of their customers who bought products for eclipse protection from merchants that can't legitimately trace what they sell. Counterfeit solar filters do exist. NASA has published a list of reputable sellers (pdf link). That doesn't mean the glasses you purchased is unsafe if it isn't on their list, but it isn't you'd better have some other way to vouch for them. If you have any questions, it's recommended that you not risk your eyesight.
Making Your Own Solar Filter
Mylar solar film can be bought for a lot less than can premade threaded solar filters. A quick Google search will yield numerous sites that publish instructions on making your own filter using mylar film from either Thousand Oaks Optical or the Baader Planetarium. Making one isn't difficult, but does require at least some attention to detail. It is important that the film lay flat in the frame. Any wrinkles in the film could result in optical distortions that spoil any images made with it. But even more important is the need to avoid damaging the film Any pinholes or light leaks at the edges could cause problems for your photography and your eyesight. The sun is bright, and yes, it can damage your vision. Looking at the sun is not something to do without proper precautions.
What About Using a Mobile Phone Camera?
You can use most any camera to shoot the eclipse, but remember that you will still need a filter. Track down some mylar solar film, cut off a small piece, and tape it over your lens. You probably won't be able to get anywhere near filling the frame with the sun's disc either. The focal length range on most mobile phones is rather limited. Telephoto adapters that clip onto a mobile phone are available, but these generally aren't noted for having very good optical quality.
How Rare is an Eclipse?
The moon makes a complete trip around the Earth over a period of roughly a month. It does this month in, month out, so it would seem as if it would pass between Earth and Sun somewhere along the way, every month. And indeed, it does. So, doesn't that mean there should be a solar eclipse every month? There would be, if the orbital plane of the moon were in aligned with that of the Earth's rotation around the sun. But the moon's orbit lies at enough of an angle that it just misses passing directly in front of the sun most months. We see a new moon when the sun is roughly behind the moon, but a solar eclipse only happens when it is exactly behind it.
Roughly twice a year though, the orbital planes intersect, and conditions are ripe for a good eclipse. When the sun and moon cross paths on the same side of the Earth, we get a solar eclipse. When their orbits line up but on opposite sides of the earth, we get a lunar eclipse. Since the earth is round and people live all over it, lunar eclipse season for one hemisphere is solar eclipse season on the opposite side of the globe. So, while we here in the United States will be treated to a solar eclipse on August 21, there was a partial lunar eclipse visible in Europe the night of August 7.
But even when the chance of an eclipse is high, you still have to be in the right place at the right time to see it. A glancing partial eclipse is not at all rare. A total eclipse of the sun near where you live most assuredly is.
Smoke Gets in Your Eye
At least here in the Northwest, we are well into forest fire season. We just ended the longest spell on record without rain, and the air quality in the Puget Sound region has been less than ideal as a result of smoke blown down from British Columbia. Driving down to Oregon to be along the path of totality doesn't mean I'll necessarily leave the forest fire smoke behind either. Oregon has had problems with forest fires too. Just one more thing to consider when settling on a location to shoot from.
It may seem odd for me to recommend planning ahead when the eclipse is just over a week away. At this point, most of your planning should already have been done. Yet many are still scrambling to track down a filter that won't risk eye damage. Since few have much experience with photographing solar eclipses, myself included, we would have been prepared months or even years ago. But even if you do have all your equipment ready to go, your preparations aren't finished yet. Charge your batteries fully the night before. And be sure to leave for your selected destination with plenty of time to spare. Near the path of totality, expect traffic to be heavier than normal. If you think you'll be heading off the beaten track to avoid all the crowds, consider that you're probably not alone in thinking this. Be sure your gas tank is full. If you have to pull over to the side of the road and settle for a partial eclipse, you won't get another shot for a full eclipse for quite a few years.