On Monday, August 21, the continental United States will experience the "Great American Eclipse". Viewers located in the narrow path of totality will see a total eclipse, during which the Moon will completely block the Sun's light for up to two minutes and forty seconds. Here in Southern California, we will be able to see a partial eclipse, in which the Moon partly blocks the Sun over a period of about two and a half hours starting at 9:06 am. This page provides information and links for everyone interested in viewing the eclipse, including important eye safety information.
What is an eclipse?
Solar eclipses happen when the Sun, the Moon, and the Earth are all aligned along a line, with the Moon in between the Sun and the Earth. The Moon casts a shadow on the Earth, and the shadow quickly sweeps across the Earth's surface as the Earth rotates and the Moon and Earth move in their orbits. In a total solar eclipse, viewers in a narrow band of locations on Earth can see the Moon briefly cover the entire surface of the Sun. See the NASA web site for an explanation of How Eclipses Work with pictures and videos, or this article that contains clear explanations and animations. The last time a total solar eclipse happened in the continental United States was in 1979, and the next one after this year will be in 2024. NASA's eclipse web site lists the dates and shows maps for the locations of past and future eclipses.
Where can I find general information about the eclipse?
Two of the best and most informative web sites are the NASA Eclipse site, and the American Astronomical Society (AAS) Eclipse site. Both of these web sites contain maps, educational information, viewing instructions, and eye safety information.
For smartphones, the Smithsonian Eclipse App has an interactive map and eclipse timing, eye safety information, and more.
Where is the eclipse happening? Where is the path of totality?
Check the NASA Eclipse web site for an interactive map. The path of totality is a narrow band running diagonally across the country from Oregon to South Carolina. Only observers within that narrow band will get to experience the glory of the total eclipse, when the moon completely covers the Sun's surface, the sky goes dark, and the Sun's corona becomes visible. Outside the path of totality, other locations in the United States will see a partial eclipse, in which the moon doesn't fully cover the Sun. At the peak of the eclipse as seen from Irvine, 60% of the Sun's disk will be covered by the Moon, so the event as seen from here will not be nearly as exciting or dramatic as a total eclipse, but a partial eclipse seen from here is still a rare and interesting event.
When does the eclipse happen in Southern California?
In Irvine, the partial eclipse begins at 9:06 am on August 21, when the Moon will just begin to cover the Sun. Maximum eclipse will be at 10:22 am, when 60.75% of the Sun will be covered by the Moon. The partial eclipse will end at 11:45 am. From other locations in Southern California, the timing will be very similar to this, with variations of just a few minutes in the start and end times across Southern California.
You can use the NASA Eclipse map to find out the exact timing of the eclipse from your location. This map lists times in Universal Time (equivalent to Greenwich Mean Time) and the page gives information on how to convert UT to your local time zone. Or, try the Smithsonian Eclipse smartphone app which will give you the eclipse timing details at your precise location, in your local time zone.
How can I view the partial eclipse safely?
Eye safety is extremely important when viewing the partial eclipse. DO NOT look directly at the Sun without using special protective equipment! Looking at the Sun, even momentarily, can cause permanent eye damage. Before the eclipse, take a few minutes to read the AAS Eclipse Eye Safety page for detailed information and instructions on how to view the eclipse safely. The AAS also provides a handy 1-page pdf on eye safety. Ordinary sunglasses will NOT protect you from eye damage if you look at the Sun.
Fortunately, you can use safe and inexpensive "eclipse glasses" with special plastic filters that block out nearly all of the Sun's light. Using eclipse glasses, you can enjoy the partial eclipse safely. Look for eclipse glasses that are certified to be compliant with the ISO 12312-2 safety standard. The AAS maintains a list of reputable vendors of eclipse glasses and other safe viewing equipment, and a lot of detailed information on what to look for. And, beware of counterfeit eclipse glasses that aren't certified for the ISO standard.
Some online retailers from this list may be out of stock as the eclipse date approaches. The AAS eclipse glasses information page also has a list of brick-and-mortar retail stores that carry certified eclipse glasses. This includes some national chains with branches in and around Irvine, but local stores are selling their inventory of eclipse glasses rapidly and might not have any in stock in the days leading up to the eclipse.
If you'll be in the path of totality for the eclipse, then only during the brief total eclipse is it safe to look at the Sun directly, when the Moon completely covers the Sun's surface. You'll still need eclipse glasses to view the partial phases of the eclipse.
Another fun way to view the eclipse is to make a pinhole projection screen. Using a pinhole projector is the safest way for young children to view the eclipse, because adult-sized eclipse glasses might not fit well on small faces. Just take a piece of cardboard or card stock (like cardboard from a cereal box) and punch or cut small round holes in it, with holes of around 1/4-inch diameter. Then, during the eclipse, hold your projection screen a few feet above the ground so that rays of sunlight go through the holes, and look at the shadow that it casts on the ground, or use it to cast a shadow on a wall. Each of the holes will project the shape of the eclipsed Sun. Here's a video that shows an example of a pinhole projection screen. You can also make another kind of pinhole viewer using a cereal box and aluminum foil: see this NASA video for easy instructions.
Where should I go to see the eclipse?
To experience the total eclipse, you have to be in the path of totality, which unfortunately is a long trip from Irvine.
If traveling to the path of totality isn't an option for you, you can view the partial eclipse from anywhere you happen to be in North America on August 21, as long as you're under clear skies and you've got your eclipse glasses or pinhole projector ready. You don't really need to be anywhere special to view the partial eclipse: just get your eclipse glasses, go outside, and enjoy the view!
For those on the UCI campus or close by on the 21st, UCI astronomy students will be setting up a viewing station on campus starting at 9 am, with a solar image projector for viewing and eclipse glasses to share with visitors. The event will be held on the Physical Sciences Plaza area, next to Frederick Reines Hall and Rowland Hall. Click here for more information and to RSVP for the viewing party.
The UCI Astronomy Outreach Program will also be hosting a partial eclipse viewing event at the UC Yosemite Field Station near Wawona inside Yosemite National Park. If you'll be at Yosemite on August 21, please join us there!
NASA TV will be broadasting a live stream of eclipse news and viewing events on August 21, and there wlll be extensive media coverage and news, so even if you can't make it to the path of totality, there will be lots of great pictures and video to look at as the eclipse occurs.