Prelude to Totality: A Final Look at the Total Solar Eclipse

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Totality! The view during the November 2012 total solar eclipse. Image credit and copyright: Sharin Ahmad (@Shahgazer)

It’s hard to believe: we’re now just one short weekend away from the big ticket astronomical event for 2017, as a total solar eclipse is set to cross over the contiguous United States on Monday, August 21st.

Celestial mechanics is a sure thing in this Universe, a certainty along with death and taxes that you can bet on. But there are still a few key question marks leading up to eclipse day, things that we can now finally make intelligent assumptions about a few days out.

Although totality slices through the U.S., partial phases of the eclipse touch on every continent except Antarctica and Australia. Credit: Michael Zeiler/The Great American Eclipse.

First up is solar activity. If you’re like us, you’ll be showing off the Sun in both visible and hydrogen alpha as the Moon begins making its slow hour long creep across the disk of Sol. First, the good news: sunspot active region AR 2671 made its Earthward debut on Tuesday August 15th, and will most likely stick around until eclipse day. The bad news is, it most likely won’t have lots of friends, as solar cycle #24 begins its long slow ebb towards the solar minimum in 2019-2020. Likewise, I wouldn’t expect to see any magnificent sprouting red prominences in the solar chromosphere in the seconds bracketing totality, though we could always be pleasantly surprised.

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The Earthward face of Sol as of August 17, four days before totality. Sunspot AR 2671 is robust and growing in complexity. Credit: NASA/SDO/HMI

How will the white hot corona appear during totality? This is the signature climax of any total solar eclipse: veteran umbraphiles can actually glance at a photo of totality and tell you which eclipse it was from, just on the shape of the corona. The National Solar Observatory released a model of what that Sun’s magnetosphere was doing one Carrington rotation (27 days) prior to the eclipse on July 25th, a pretty good predictor of the corona might look like during those fleeting moments of totality:

Solar Corona
The shape of the field lines of the solar corona, one rotation prior to the August 21st total solar eclipse. Credit: The National Solar Observatory.

NASA will be chasing the umbra of the Moon with two converted W-57 aircraft during the eclipse, hoping to unlock the “coronal heating paradox,” image Mercury in the infrared, and hunt for elusive Vulcanoid asteroids near the eclipsed Sun.

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The view of the corona during totality? This computational model was derived from NASA SDO data during the last solar rotation. Credit: Predictive Science Inc.

The corona is about twice as bright as a Full Moon, and its interface with the solar wind extends out past the Earth. The very onset of totality is like the footstep of a giant passing over the landscape, as the door of reality is suddenly ripped open, revealing the span of the glittering solar system at midday. Keep your eyes peeled for Mercury, Venus, Mars, Jupiter and twinkling Regulus tangled up in the corona, just a degree from the Sun-Moon pair:

The line up of the planets, bright stars and the eclipsed Sun during totality at 2:37 PM EDT as seen from Franklin, North Carolina. Credit: Stellarium.

Also, be sure to scan the local horizon for a strange 360 degree sunset as you stand in the umbra of the Moon. An “eclipse wind” may kick up, as temperatures plummet and nature is fooled by the false dawn, causing chickens to come home to roost and nocturnal animals to awaken. I dare you to blink. Totality can affect the human heart as well, causing tears to cries of surprise.

Here’s an interesting, though remote, possibility. Could a sungrazing “eclipse comet” photo bomb the show? Karl Battams (@SungrazerComets) raises this question on a recent Planetary Society blog post. Battams works with the Solar Heliospheric Observatory (SOHO), which has discovered an amazing 3,358 comets crossing the field of view of its LASCO imagers since 1995. Comets have been discovered during eclipses before, most notably in 1882 and 1948. To be sure, it’s a remote possibility this late in the game, but Battams promises to give us one last quick look via SOHO the morning of the eclipse on his Twitter feed to see if any cometary interlopers are afoot.

The possible search area for Kreutz group sungrazers during the August 21st eclipse. Credit: Karl Battams.

Now, on to the biggest question mark going into this eclipse weekend: what’s the weather going to be like during the eclipse? This is the ever-dominating factor on everyone’s mind leading up to eclipse day. Keep in mind, the partial phases are long; even a partly cloudy sky will afford occasional glimpses of the Sun during the partial phases of an eclipse. Totality, however, is fleeting – 2 minutes and 40 seconds near Hopkinsville, Kentucky and less for most – meaning even a solitary cumulus cloud drifting across the Sun at the wrong moment can spoil the view. No weather model can predict the view of the sky to that refined a level. And while best bets are still out west, lingering forest fires in Oregon are a concern, along early morning fog on the western side of the Cascade Mountains. Michael Zeiler over at The Great American Eclipse has been providing ESRI models of the cloud cover over the eclipse path for Monday… here’s the outlook as of Thursday, August 17th:

A look at cloud cover prospects over the eclipse path as of August 17. Credit: Michael Zeiler/Great American Eclipse/ESRI.

Computer models should begin to come into agreement this weekend, a good sign that we know what the weather is going to do Monday. Needless to say, a deviation from the standard climate models could send lots of folks scrambling down the path at the last minute… I’ve heard of folks with up to 5 (!) separate reservations along the path of totality, no lie…

The NOAA also has a fine site dedicated to weather and cloud coverage across the path come eclipse day, and Skippy Sky is another great resource aimed at sky viewing and cloud cover.

Clouded out? The good folks at the Virtual Telescope have got you covered, with a webcast for the total solar eclipse starting at 17:00 UT/1:00 PM EDT:

Credit: The Virtual Telescope Project.

Of course, you’ll need to use proper solar viewing methods during all partial phases of the eclipse. This means either using a telescope with a filter specifically designed to look at the Sun, a pin hole projector, or certified ISO 12312-2 eclipse glasses. If you’ve got an extra pair, why not convert them into a safe filter for those binoculars or a small telescope as well:

Also be wary of heatstroke, standing out showing folks the partially eclipsed Sun for an hour or more. It is August, and heat exhaustion can come on in a hurry. Be sure you have access to shade and stay cool and hydrated in the summer Sun.

Finally, eyes from space will be watching the eclipse from the International Space Station as well. Looking out at Monday, the ISS will pass through the penumbra of the Moon and see partial phases of the eclipse three times centered on 16:32, 18:20, and 20:00 Universal Time. The center time is particularly intriguing, as astros have a chance to see the dark umbral shadow of the Moon crossing the central U.S. This also means that eclipse viewers on planet Earth around southern Illinois might want to glance northward briefly, to spy the ISS during totality. Also, viewers along a line along southern central Canada will have a chance to catch an ISS transit across the face of the partially eclipsed Sun around the same time. Check CALSky for details.

Three passes of the International Space Station versus the path of of totality. The inset shows the view of the partially eclipsed Sun as seen from the ISS. Credit: NASA/JSC.

We’ll be at the Pisgah Astronomical Research Institute in southwestern North Carolina, for a glorious 104 seconds of totality. We expect to be out of wifi range come eclipse day, but we’ll tweet out key eclipse milestones as @Astroguyz. We also plan on writing up the eclipse experience with state-by-state testimonials post eclipse.

Perhaps, the August 21st total solar eclipse will bring us all together for one brief moment, to witness the grandest of astronomical spectacles. We’re lucky to share a small patch of time and space where total solar eclipses are possible.  Good luck, clear skies, and see you on the other side early next week!

Webcasts and Forecasts for Tonight’s Total Lunar Eclipse

Are you ready for some eclipse action? We’re now within 24 hours of the Moon reaching its ascending node along the ecliptic at 13:25 Universal Time (UT)/ 9:25 AM EDT on Tuesday morning and meeting the shadow of the Earth just over seven hours earlier.

We’ve written about viewing prospects for tonight’s lunar eclipse. This eclipse is the first total lunar eclipse since December 10th, 2011 and is the first in a series of four — known as an eclipse tetrad — visible from North America in 2014 and 2015. Totality lasts 1 hour and 18 minutes and falls just 29 minutes short of the theoretical maximum, which was last neared on January 21st, 2000 and won’t be topped until July 27th, 2018.

This will be an early morning event for U.S. East Coasters spanning 2:00 to 5:30 AM local (from the start of the partial umbral phases and totality), and a midnight spanning-event for the Pacific coast starting at 11:00 PM Monday night until 2:30 AM Tuesday morning on the 15th.

And as always with celestial events, the chief question on every observer’s mind is: will the skies be clear come show time? Should I stay put, or ponder going mobile?

When it comes to astronomical observing, a majority a mainstream weather resources only tell part of the story, often only listing cloud cover and precipitation percentages. Seeing, transparency, and low versus middle and high cloud decks can often mean the difference between a successful observing session and deciding to pack it in and watch Cosmos reruns online. But the good news is, you don’t need crystal clear skies to observe a total lunar eclipse, just a view of the Moon, which can easily “burn through” a high cirrus cloud deck. We’re going to share a few sites that are essential tools for planning an observing session and what they say about the prospects for seeing tonight’s eclipse.

Cloud cover prospects. Credit: NOAA.
Cloud cover prospects towards the end of tomorrow morning’s lunar eclipse. Credit: NOAA.

Now the bad news: things aren’t looking good for eastern North America. In fact, the dividing line between “cloudy” and “clear” runs right down through central Ontario and follows the Mississippi River at mid-eclipse, which occurs at 7:47 UT/3:47 AM EDT. There’s a high pressure front sweeping eastward, bringing rain and cloudy skies with it. The Florida peninsula and parts of New England and the Canadian Maritimes may have shots at viewing the eclipse through partly cloudy skies.

The National Oceanic and Atmospheric Administration maintains a great interactive site with graphical interactive forecasts, to include satellite maps. Another long-standing source of good info is the Weather Underground. For tailor-made astronomy forecasts, we’re checking Clear Sky Chart (formerly Clear Sky Clock) and SkippySky daily for upcoming prospects. A great feature in SkippySky is that it not only gives you cloud cover maps, but layers them with high versus middle and low clouds… again, a thin high cloud deck during the lunar eclipse could still mean game on!

Clouded out? There’s a half dozen webcasts planned for tonight’s lunar eclipse as well.

Dependable Slooh will have a live broadcast with commentary on the eclipse starting at 2AM EDT/6:00 UT:

Also, our good friends at the Virtual Telescope Project will be covering the lunar eclipse as part of their ongoing Global Astronomy Month campaign and will utilize several North American observers to cover the event:

NASA is also planning a broadcast out of the Marshall Space Flight Center of the eclipse along with a discussion on Reddit with NASA planetary scientist Renee Weber also starting at 2:00 AM EDT:

Video streaming by Ustream

The Coca-Cola Space Science Center and Columbus State University also plans host a webcast of the lunar eclipse starting at 3:00 UT/11:00 PM EDT.

Also, the PBS Star Gazers project is planning on hosting a broadcast of the eclipse starting at 1:30 AM EDT/5:30 UT:

Video streaming by Ustream

And finally, we hope to launch our very own initiation into the world of eclipse webcasting with an hour-long broadcast of the crucial phase transition from partial to total eclipse starting at 2:30 AM EDT/6:30 UT, weather willing:

Live streaming video by Ustream

And hey, word is that doomsday purveyor John Hagee is planning a broadcast of a more “End of the World” bent tonight as well. We didn’t know he was an astronomy fan…

Prospects call for a brighter than normal eclipse, as atmospheric sciences professor at the University of Colorado Richard Keen notes that the Earth’s stratosphere is currently relatively clear of dust and volcanic ash. Still, we’ve been surprised before. The darkness and color of the eclipsed Moon is expressed on what’s known as the Danjon scale. As during eclipses previous, we’ll be data-mining Twitter for estimates and averages to see how they stack up… tweet those observations to #DanjonNumber.

Opportunities to catch the ISS transiting the Moon... during tonight's eclipse. Credit: CALSky.
Opportunities to catch the ISS transiting the Moon during tonight’s eclipse. Credit: CALSky.

We also ran the possibilities for catching a shadow transit of the International Space Station in front of the eclipsed Moon for North American observers. To our knowledge, this has never been done before. Live near one of the two paths depicted above? You may be the first to accomplish this unusual feat.   Check in with CALSky for specifics.

Our backyard "eclipse broadcasting station."
Our backyard “eclipse broadcasting station.”

Finally, ever wonder when the next eclipse will occur during the Sunday night Virtual Star Party? If you’re like us, you consider and ponder such astronomical occurrences… and it turns out, the very last lunar eclipse in the current tetrad next year on September 28th, 2015 does just that. And stick around until July 13th, 2037 and we’ll have the first ever total solar eclipse occurring during the show… we just need someone in Australia to stream it!

Tonight’s eclipse is number 56 of saros 122. Reader Rob Sparks notes that the last eclipse (55) in this series occurred on April 4th 1996 and also hosted an extra-special celestial treat, as Comet Hyakutake was just beginning to put on its memorable performance.

In short, don’t fear the “Blood Moon,”  but do get out and catch tonight’s fine lunar eclipse… we’ll be doing a post-eclipse photo roundup tomorrow, so be sure to send those pics in to Universe Today!