27 March 2014

Preview of the Aug 21, 2017 Total Solar Eclipse

August 2017 Eclipse Path
I am a fan of total solar eclipses, and although it is a long time in the future, I want to provide some resources for those who want to learn about an incredible eclipse that will cross the entire North American continent in August of 2017. This summertime spectacle tracks from the Oregon coast to South Carolina and affords good views for up to 2 minutes and 40 seconds of breathtaking totality. The summer climate is mostly reliable along the eclipse track and the interstate freeway system ensures that local climate problems will be manageable should there be inclement weather in spots along the eclipse path. Here are some of the best online resources for planning to see the eclipse that I have found so far:

NASA's Eclipse Resource Center
Eclipse Chasers

Each of these sites offer tips and suggestions for getting to the right place and being ready for seeing an eclipse. Since weather plays such a critical role in the success or failure of an eclipse expedition, you'll need to carefully study Jay Anderson's excellent analysis. Jay is a legendary eclipse chaser and I was on his mission in 1991. I have come to respect his analysis as the best around.


firstmagnitude said...

The maximum duration for August 21, 2017 will be near Goreville Illinois with darkness lasting 2 minutes and 41.6 seconds (you can see this on Xavier Jubier's eclipse map as a green dot (http://xjubier.free.fr/en/site_pages/solar_eclipses/TSE_2017_GoogleMapFull.html). NASA's Fred Espenak, last month, rewrote the definition of greatest eclipse (GE) to where he does not include the term greatest duration (GD) in that definition but separately (http://eclipse.gsfc.nasa.gov/SEhelp/SEglossary.html).

The location of greatest duration and greatest eclipse are now over 100 miles apart (as can be seen from Jubier’s map). This has been known for several years, but NASA's solar eclipse website did not reflect the newer findings until just last month in February. I wasn’t aware of this until last year. I always assumed GD and GE meant basically the same thing. The old definition did state that GE and GD were “virtually” in the same spot on the map.

Hopkinsville Kentucky was considered the prime location for the 2017 solar eclipse, because of it being a large town of some 20,000 people, and it being within fifteen miles of GE (which is actually near Cerulean Kentucky). However, Michael Zeiler, of http://www.eclipse-maps.com/Eclipse-Maps/Welcome.html , said to look at southern Illinois for GD. He specifically states an area a few miles west of Goreville Illinois in the Shawnee National Forest. This new location is a thirty minute drive from Carbondale Illinois.

Having written all of this, we now come to the United States Naval Observatory (USNO). They do not recognize the term “greatest eclipse” or “greatest duration.” They use the term “maximum duration.”

When I was growing up, and before the NASA eclipse website showed-up, I used to always use The American Ephemeris and Nautical Almanac (currently The Astronomical Almanac) for my eclipse information. Lately, I have become lazy, and I started using NASA’s eclipse website.

For 2017, USNO states that the maximum duration (note that I don’t use GD) will be six miles south of Carbondale Illinois http://aa.usno.navy.mil/data/docs/Eclipse2017.php . The astronomer I wrote to at USNO states that, “We compute a longest duration on the central line of 2 minutes 44.6 seconds…” This is a good four seconds longer than what Espenak/NASA first calculated.

So who’s eclipse information do we use – NASA or USNO? As I mentioned earlier, I use to always use USNO for eclipse maps and data. They have been around since the 1800s. I have always found them to be very accurate (and I still do), and they are staffed with fulltime astronomers.

As for NASA, Fred Espenak retired in 2009. NASA now considers Fred Espenak a “volunteer” and the solar eclipse website is a platform that NASA generously allows Espenak to use. NASA does not have a department or staff dealing with eclipse information.

So again, who do we use? Who do we recognize? Currently, I am using NASA’s information, because the data at NASA’s website has been rewritten, somewhat last month, to reflect the changes. Xavier Jubier’s map shows this change, as well as, showing GD and GE separately.

I would like to use USNO’s information, but I find their maps lacking in detail. I feel they need to spend more time outreaching to the public for this special USA celestial event. But I do like those four extra seconds that USNO calculated, and for a solar eclipse, every second counts.

I have asked Xavier Jubier would he be willing to meet with USNO to see if they can work out their differences. Jubier said no. He felt his calculations were correct. Jubier said Espenak is using his software. I hadn’t asked USNO yet.

So this is the state of affairs of the August 21 2017 eclipse as of March 28 2014. The information is not set in concrete as of yet. You can see the latest at my website http://shadowandsubstance.com/2017/2017e.html, or for iPad users, http://www.kysolareclipse.org/ . I live in Kentucky, and I head the solar eclipse committee at the Western Kentucky Amateur Astronomers http://wkaa.net/index.php#.UzXTrE1OVdg .

JonT said...

Im so excited my property is on the direct line in southern illinois in vienna Just southeast of carbondale
It will be awesome just pray for clear skies