The scientific community in general, and astronomy in particular, is all abuzz these days as the hype builds for the upcoming North American Eclipse, happening on August 21. Between my position here at B&H and my personal interest in astronomy, I’ve been talking about this event for almost a year to my friends and colleagues, and I’ve found that people have a lot of questions about solar eclipses. Sure, we’ve all heard about solar eclipses, but how many of us have actually done research on them? I’m thinking that the answer is “not many.” And I don’t blame you. Solar eclipses usually happen over the oceans or in sparsely populated areas, so they don’t attract a lot of attention—but this upcoming eclipse is something of a unicorn in that it’s traversing the entire United States, from coast to coast. For context, this hasn’t happened in more than 100 years. In the spirit of answering some of the questions you didn’t know you had about solar eclipses, I’m here to share with you the 15 most frequently asked questions I get about this awe-inspiring event.
1. What’s the difference between a Lunar and Solar eclipse?
The sun is at the center of our solar system, and the Earth orbits it. The moon, in turn, orbits the Earth. The moon is visible to us because it reflects the sun’s light from its surface, effectively making it a big reflector. Now, with everything spinning around everything else, eventually the sun, Earth, and moon will align precisely to cause an eclipse. When Earth is perfectly aligned between the sun and the moon, we have a lunar eclipse—the moon is eclipsed by Earth—and this happens only at night. A solar eclipse happens only during the day, and occurs when the moon is aligned between the sun and Earth. Now, because the moon is so much smaller than Earth, the shadow it casts is relatively small, so there is what is called a “path of totality,” which will be several miles wide.
2. Is this really a big deal?
Yes. Yes, it is. If you live anywhere near the path of totality, there will be people EVERYWHERE. Don’t assume you’ll be able to go to your favorite park an hour before the eclipse and put out a blanket and have a picnic. Check with your local government or Chamber of Commerce and find out if there will be designated viewing locations.
3. Will I really go blind if I look at the Sun?
The short answer is: “Yes.” The more comprehensive answer is that there are two kinds of damage that can occur by looking at the sun—short-term and long-term. Short-term damage, or “solar retinopathy,” is a result of too much ultraviolet light flooding the retina. In extreme cases, this can cause blindness, but is so painful that it is rare for someone to be able to stare at the sun long enough for that to happen. Typically, eye damage from staring at the sun results in blurred vision, dark or yellow spots, pain in bright light or loss of vision in the center of the eye. The retina does not have pain sensors, so you will not know that you are experiencing long-term eye damage, and permanent damage has been shown to occur in less than two minutes. The bottom line is: Don’t stare at the sun.
4. Where and when can I view it?
Check out this interactive map that NASA created, and it’ll show you the path of the eclipse with times of totality and duration.
5. How long will the eclipse last?
This depends entirely on where you are when totality occurs. The point of Maximum Duration, the longest amount of time the sun will be eclipsed at any point during the entire event, located about 100 miles SE of St. Louis, MO is 2m 40.2s. Anywhere else will experience a shorter duration.
6. What will I see if I’m not in the path of totality?
Most of North America, out of the path of totality, will see a partial eclipse. The percentage greatly depends on where you’re located. Seattle will experience 92% obscuration, Los Angeles: 62%, Las Vegas: 71%, Dallas: 75%, Chicago: 87%, Atlanta: 97%, and New York City: 71%. So, even if you’re far from the main event, it’s still going to be awesome.
7. Do I still need to protect my eyes if I’m in an area that’s only getting a partial eclipse?
Even more so. The only time you can look directly at the sun is for the brief period of totality. So, no matter where you are for the eclipse, you need to wear proper eyewear.
8. The whole family is going! Should we bring the dog?
Animals will absolutely be scared by the eclipse, and you will want to be enjoying it instead of trying to calm your crazed critters. Do yourself and everyone around you a favor and leave them at home.
9. How do I know if my filter is defective?
Simply take a bright flashlight and shine it through the filter. If you see light, then the filter should be replaced. Under no circumstances should you use a defective filter.
10. My kids will be in school during the eclipse… won’t their science teacher take them out and show them?
Don't count on it. Remember that schools must be careful about liability these days, so they probably won’t allow kids to watch the eclipse, because of the off-chance that a student will stare at the sun without filters and blind him/herself. More likely, they’ll be sequestered in a windowless room watching a movie.
11. The Sun’s out! How do I polar-align my scope during the day?
Most GoTo systems will have the sun as an alignment star, so that’s easy. It gets a little tricky for a manual EQ mount, since proper polar alignment is critical to accurate tracking of any manual or motorized mount you need to get it right, but you can’t see Polaris during the day. Ideally, you could go out the night before the eclipse, set up your rig, and polar-align it as normal. When it’s precisely aligned, mark the spot where your tripod is set up with stones or pavers to show where to place the tripod during the day, then make note of the settings on the axes and replicate them when you set up for the eclipse. Other methods involve determining the magnetic offset degree between True and Magnetic North, setting up a compass and then using that known degree value to align the mount. A common way of doing this is with a board marked with where to put the tripod legs, and alignment markings. I suggest Googling the “Drift Method’ for details.
12. What’s the First Bite, and what happens?
It’s going to sound silly, but here’s what happens… there’s a lot of anticipation leading up to the start of the eclipse. The first person who spots the start of the eclipse—the first “bite” out of the sun—that person yells, “First Bite!” It’s silly and meaningless… but fun, nonetheless!
13. What’s the “Diamond Ring” Effect?
This is what everyone will be talking about before, during, and after. Moments before totality, the Moon will be covering most of the Sun and the corona will be seen around it edges (a ring) and right before totality a small part of the Sun will be visible and will flare as totality occurs (like a diamond on the ring).
14. Close to the path of totality is close enough, right?
I guess, if you don’t want to see a total eclipse. Unless you’re right IN THE PATH, you won’t see the Good Stuff, and might walk away disappointed. If you are close to the path of totality, GET in the path.
15. It was cloudy and I couldn’t see the eclipse! Will I ever see another?
Guess what? You’re in luck! North America will be experiencing another total solar eclipse on Monday, April 8th, 2024. It will take virtually a mirror path to the 2017 path, so mark your calendars!