Safe Solar Viewing

With a solar eclipse crossing the North American continent on August 21st, lots of us will be spending time staring at the sun. Don't get caught short in a last minute rush of eager eclipse watchers. Choose how you will safely view the sun and get the devices or supplies you need now.

We all occasionally glace directly at the sun without any immediate damage beyond that black spot that fades after a half hour or so. Assuming that a nice dark pair of sunglasses will be all you need for viewing the eclipse is risking blindness. The eclipse is interesting and it's natural to look for much longer than the brief glances we get in daily life. Sunlight also has substantial amounts of invisible infrared and ultraviolet lite that can blind us invisibly.

I've written before about sun safe white light filters for telescopes. Today's note covers viewing with just your eyes or binoculars. Filters for binoculars are similar to those for telescopes, except that you need two of them. You can get them commercially from the same sources as telescope filters, or make your own using plastic solar filter sheets.

You can also find or make projection devices for viewing the sun indirectly as simply as punching a hole in a piece of cardboard. Be sure to read NASA's advice on Eye Safety During a Total Solar Eclipse. Some common options for direct viewing with just your eyes are shown below:

Welders glass #15 is safe for looking at the sun; easy to find and inexpensive. I cover the edges of the glass with plastic tape to protect from cuts. Many welding goggles are sold with #5 glass, these are NOT safe for looking at the sun. Make sure that they are at least #14 glass or a solar film specifically certified as safe for visual observation of the sun. Sun safe solar filter film is available as inexpensive cardboard eyeglasses and rectangular cards. I find that the cardboard glasses get uncomfortable quickly and are hard to share. The rectangular cards are easy to share with friends with or without glasses. All of these options are available for less than a couple of dollars. More comfortable sunglasses style options are available, but for about the same price the option below lets you see a lot more. My mini-review follows:

Lunt Mini Sunoculars are about the same price as comfortable sunglasses style eye protection safe for direct solar viewing. They will show you a lot more detail. They are 6X30mm with 9mm of eye relief and adjust for an eye spacing of 56-71mm.

The solar filter is built in and gives a nice yellow-orange sun. One of my eyes is very near sighted and the eyepiece focus adjustment was enough to accommodate it. With eyeglasses on there was enough eye relief for a good view.

With the built in solar filer, everything other than the sun is black, so it took a moment to get it in the field of view. The FOV is about 3 degrees. The image appeared sharp and the advertised 6x larger. There were only small sunspots are on the sun today and I wasn't able to pick them out with these. I'm confident that mid to large size sunspots will show up well. They are very light and easy to hold steady.

I think that these will be great to have at at the eclipse and for viewing mid to large sunspots. They won't do you any good during totality, but regular binoculars or just your eyes are what you want then. They were less than $30 and I've seen them at B&H Photo, Amazon, and the ASP solar eclipse shop.

Content created: 2017-03-02 and last modified: 2017-03-04

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