2024 total solar eclipse: The novelty of "the cross"
By
Dr. Gordon Telepun
Published Apr 7, 2020 5:02 PM EDT
This astronomy blog was written by Dr. Gordon Telepun, an expert eclipse photographer and eclipse educator and the developer of the solar eclipse timing app Solar Eclipse Timer.
The intersection of the paths
In just 4 years, on April 8, 2024, a total solar eclipse will cross the United States, and at some point, you will read an article that states something like “a spot on the Earth will witness a total solar eclipse approximately every 375 years.” This basically means that if you want to witness a total solar eclipse, you will most likely have to travel to “it” and not wait for “it” to come to you! That is why people who love total solar eclipses, called “eclipse chasers” or “umbraphiles,” travel the world to position themselves in the path of totality. But the 375 years is the mean frequency of a spot on Earth witnessing an eclipse, so in reality, for some lucky locations, the years of waiting is much shorter.
The U.S. was in the path of the 2017 total solar eclipse, and in 2024, it’s in the path of another total solar eclipse. These two eclipse paths intersect in southern Illinois (Figure 1).
Figure 1. The U.S. is lucky enough to contain the paths of two total solar eclipses separated by only 6 years, 7 months and 18 days!
For some eclipse chasers, this creates an interesting challenge, the novelty of observing both of these eclipses somewhere in “the cross.” When the two paths are overlaid and viewed up close, they create a shape that is basically an irregular quadrilateral (not exactly due to curves lines) with the sides formed by umbras that are approximately 71 by 115 miles wide. This creates a region of land, touched by umbra, which totals approximately 8,165 square miles. (Figure 2)
Figure 2. The umbra widths for the two eclipses at the intersection. The majority of “the cross” is in southern Illinois.
Anywhere in this irregular region of land would allow witnessing both total eclipses. But of course, eclipse observers want to maximize their totality duration by being close to the center line, so the entire region is not useful. Let’s arbitrarily limit the observing area on each side of the center line to 20 miles and do this for both eclipses. This creates two different 40 mile wide observing zones for the two eclipses. We have to simulate the prime observing region by overlapping these two square observing zones centered at the intersection of the center lines. The area contained within both of the boxes provides the longest totality durations while observing both eclipses at “the cross” and this region of land now becomes less than 1,600 square miles. (Figure 3)
Figure 3. For eclipse observers who successfully witnessed the 2017 eclipse inside of the yellow box, they can try to witness the 2024 eclipse inside the red box to witness both at “the cross” and maximize their totality duration. (Boxes are approximately 40 miles square)
The precise intersection point of the two center lines varies slightly depending on the interactive map used to simulate the two eclipses. The point is southwest of Carbondale, Illinois, and appears to be located on private property slightly removed from the east side of the shoreline of Cedar Lake. At this point the maximum totality, duration for the eclipses could have been 2 minutes and 40 seconds in 2017 and could potentially be 4 minutes and 8 seconds in 2024. However, if located along the edges of the square boxes, the totality duration time would have decreased to approximately 2 minutes and 16 seconds in 2017 and should be approximately 3 minutes and 52 seconds in 2024.
Why are we so lucky and what caused “the cross?”
The fact that we can discuss this eclipse intersection, in some respects, is lucky because it has to do our present circumstances. We are simply the beneficiaries of two things: First, we just happen to live on the continent where the umbras will travel on the surface of the Earth. Second, we are alive at this point in time. We have these two eclipses because of the wonderful repeating clockwork of the solar system. This repeating clockwork concerning eclipses is called the saros. The term saros, from its ancient origins, describes a measure of time. When applied to our understanding of eclipses, the measure of time is 6,585.3211 days, which is called one saros cycle. The orbit of the Moon around the Earth has a complex gyration as both of them orbit the Sun and this gyration has a pattern that eventually repeats itself. So on a day when the Sun, Moon, and Earth are in an alignment that creates a total eclipse on Earth, a very similar total eclipse will be created 18 years, 11 days and 8 hours in the future. This is because the Moon and Earth have returned to the same orbital positions at the end of a saros cycle and they create a very similar eclipse path.
There are many saros series in progress at this time. The 2017 eclipse belongs to saros series 145. The 2024 eclipse belongs to saros series 139. The beautiful elongated paths of these eclipses have overlapped each other many times in the past and they will overlap each other many more times in the future. So “the cross” that we are enjoying was already enjoyed in Europe, across Turkey, in 1999 and 2006. (Figure 4)
Figure 4. Because of repeating saros cycles a similar cross of eclipse paths was enjoyed by Turkey in 1999 and 2006. Saros series 145 and 139, respectively.
There are two things that complicate any repeating saros cycle a bit more. The first is that the timing of the Moon and Earth gyration combined with the Earth’s rotation moves each subsequent eclipse path in a saros about 120 degrees to the West. That is why the same set of crossing eclipses that happened in Turkey now ends up in the U.S. (Figure 5). The second thing that varies in a repeating eclipse is the latitude changes slowly, moving southward or northward, depending on whether the eclipse occurs on an ascending or descending node of the Moon’s orbit. This is why a saros series eventually ends.
Figure 5. The two eclipse paths that cross in the U.S. These occur about 120 degrees to the West of the similar paths that occurred in Turkey in the past.
When these two eclipses move west again, in 2035 and 2042, observing them will be more difficult because the paths will cross over the Pacific Ocean (Figure 6).
Figure 6. Now located about 120 degrees to the west of the continental U.S., these two eclipses cross once again, but it occurs over the Pacific Ocean.
When a saros cycle repeats three times (54 years), the longitude progression has moved about 360 degrees, so the eclipse returns to the same region of the globe. In 2053, after three cycles, the eclipse of saros series 145 returns to the region of eastern Europe, but its latitude moves south. In 2078, after three cycles, the eclipse of saros series 139 returns to North America, but its latitude also moves south. Now that you understand the idea of the saros, you can appreciate that another eclipse chasing trivial pursuit is to observe different eclipses from the same saros series. You also realize to do this, because of the longitude shift, requires international travel. My first total eclipse was from saros series 127 on June 21, 2001, across Zambia, Africa. In 2019, I witnessed the eclipse in Argentina which was also from saros series 127. In 2024, when I observe the eclipse in the U.S., saros series 139, it is from the same saros series as the eclipse I witnessed on a ship in the Mediterranean Sea on March 29, 2006.
For additional stories about what the saros means to other eclipse chasers, I recommend this article by Jamie Carter found here.
What is your priority for 2024?
Although the discussion of observing the 2017 and 2024 eclipses in the region of “the cross” is technically interesting, remember that achieving this feat is secondary to seeing the total eclipse of the Sun and witnessing the corona. (Figure 7)
Figure 7. The spectacular 2017 corona as imaged from southeastern Tennessee. High dynamic range processing of four corona images and a fifth image for Moon glow.
The 2024 eclipse occurs on Monday, April 8. This is a time of year when no region of the country along the path is safe from bad weather. The future predictions for chances of clear skies for the 2024 eclipse put the best prospects in the Southwest and not at the point of “the cross.” And as you travel further to the northeast, the percent risk of cloud cover increases. (Figure 8)
Figure 8. Cloud cover risk prediction is incredibly helpful for eclipse planning. Jay Anderson, at the website Eclipsophile, is an expert at compiling and analyzing historical data. But on eclipse day in April, any place along the path in the U.S. could be at risk.
Carbondale has been advertising itself as the town in the path of both eclipses since well before the 2017 eclipse, and that’s fine because it is definitely exciting. And I am certain that the city leaders and the residents will do an excellent job preparing for and hosting the influx of eclipse observers who will come to their town (Figure 9). It will be similar to the success that Hopkinsville, Kentucky, had when they advertised themselves as the town that was Point of Greatest Eclipse for the 2017 eclipse.
Figure 9. The town of Carbondale, Illinois, certainly does have the distinction of being the major town in “the cross.” But you pick a final observing position for eclipse day based on the weather.
However, there is a YouTube video taken during the 2017 eclipse from Carbondale, at Salukis Stadium on the campus of Southern Illinois University, where thousands of people were gathered, but were clouded out and did not see totality. This was because that specific location had clouds in the sky in front of the eclipse right at the time of totality. So you must be mobile on eclipse day, even if it means moving just 10 or 20 miles for clear skies.
In 2017, I was corresponding with a lady from Missouri who lived in the path of totality and was excited about that and planned a big eclipse viewing party for family and friends in her backyard. Unfortunately, a large portion of Missouri had storms on eclipse day and this poor lady and her guests got completely clouded out.
Therefore, if you live in the path of the 2024 eclipse, that’s great, it can be your primary observing position, but you must have alternative observing positions. Please DO NOT plan a party at your house for eclipse day! Stay mobile on eclipse day. Plan your party for a couple of weeks later when you can share stories about your successful eclipse observations. (Figure 10)
Figure 10. The country had fairly good skies on eclipse day in 2017. The worst cloud cover was over northwestern Missouri, northeastern Kansas and eastern South Carolina.
Using the Solar Eclipse Timer app in 2024
Of course, the Solar Eclipse Timer app is ready to time the 2024 eclipse, but there are some interesting things to do before that. The formula to calculate the contact times is built into the app, the data set for the completed 2017 eclipse is still present and the data set for the 2024 eclipse is available. The app does not consider the calendar day, so all observing positions in the United States can be simulated for both eclipses. This is true whether you are in the path of totality or anywhere else in the country in the area of a partial eclipse. As you can see from Figure 11, the entirety of Canada and the U.S. fall within the penumbra, an area where some portion of a partial eclipse can be observed.
Figure 11. The huge limits of the penumbra also move across the U.S., providing the entire country with the ability to see some portion of a partial eclipse, with the exception of Hawaii.
So no matter where you live in the U.S., you can use your device to geolocate and see what your partial eclipse percent obscuration would be for both eclipses. Figure 12 shows the data if you were located at Kennedy Space Center in Florida, which is out of the path of totality for both eclipses.
Figure 12. The same observing position, Kennedy Space Center, has different maximum depths of the partial eclipse due to the difference in the distance away from the center line for the two eclipses. For 2017, maximum coverage gets to 86%. For 2024, maximum coverage gets to 56%.
If you happen to live in the path of the 2024 eclipse, you can geolocate and see what your contact times and totality duration will be. Remember, if you live in the path your residence can be your primary observing site, but you must plan for alternate sites to stay clear of clouds. When planning ahead for alternate observing sites in 2024, you can manually enter the coordinates into the app and calculate the contact times for a position and then save that alternate position for analysis or a site visit later.
Figure 13. The same observing position in “the cross” in Carbondale, Illinois, has different contact times and different totality durations due to the elements of the two eclipses.
So for the 2024 eclipse, if you are observing in “the cross,” make sure you load the correct eclipse data set on eclipse day! The data set for 2017 will still calculate contact times but they will be completely wrong!
Summary
This article presents the basis for understanding why the U.S. is in the path of two eclipses just seven years apart. If the subject of the Moon’s orbit, the saros and how a saros series progresses interests you, more technical explanations can be found in other resources. The 2024 eclipse presents wonderful opportunity to witness a total solar eclipse, without international travel, and I implore you to make all efforts necessary to get to the path!
Author bio
Dr. Gordon Telepun is a plastic surgeon who lives in Alabama. He is an expert eclipse photographer and eclipse educator. He is the developer of the mobile app Solar Eclipse Timer which is designed so he can be your personal guide and photography assistant through the stages of an eclipse. The app geolocates to calculate the precise contact times of an eclipse. It does audible countdowns to the contact times and max eclipse, announces when to observe for various partial phase phenomena and automatically calculates the clock times needed to achieve a perfect eclipse sequence image. It’s especially helpful for a total eclipse but it also has a partial eclipse timing mode.
Detailed eclipse educational videos can be found on his YouTube channel called Solar Eclipse Timer
Other eclipse information including details about the app is available on his website
Contact Dr. Telepun at: foxwoodastronomy@gmail.com
Report a Typo
Weather Blogs / Astronomy
2024 total solar eclipse: The novelty of "the cross"
By Dr. Gordon Telepun
Published Apr 7, 2020 5:02 PM EDT
This astronomy blog was written by Dr. Gordon Telepun, an expert eclipse photographer and eclipse educator and the developer of the solar eclipse timing app Solar Eclipse Timer.
The intersection of the paths
In just 4 years, on April 8, 2024, a total solar eclipse will cross the United States, and at some point, you will read an article that states something like “a spot on the Earth will witness a total solar eclipse approximately every 375 years.” This basically means that if you want to witness a total solar eclipse, you will most likely have to travel to “it” and not wait for “it” to come to you! That is why people who love total solar eclipses, called “eclipse chasers” or “umbraphiles,” travel the world to position themselves in the path of totality. But the 375 years is the mean frequency of a spot on Earth witnessing an eclipse, so in reality, for some lucky locations, the years of waiting is much shorter.
The U.S. was in the path of the 2017 total solar eclipse, and in 2024, it’s in the path of another total solar eclipse. These two eclipse paths intersect in southern Illinois (Figure 1).
Figure 1. The U.S. is lucky enough to contain the paths of two total solar eclipses separated by only 6 years, 7 months and 18 days!
For some eclipse chasers, this creates an interesting challenge, the novelty of observing both of these eclipses somewhere in “the cross.” When the two paths are overlaid and viewed up close, they create a shape that is basically an irregular quadrilateral (not exactly due to curves lines) with the sides formed by umbras that are approximately 71 by 115 miles wide. This creates a region of land, touched by umbra, which totals approximately 8,165 square miles. (Figure 2)
Figure 2. The umbra widths for the two eclipses at the intersection. The majority of “the cross” is in southern Illinois.
Anywhere in this irregular region of land would allow witnessing both total eclipses. But of course, eclipse observers want to maximize their totality duration by being close to the center line, so the entire region is not useful. Let’s arbitrarily limit the observing area on each side of the center line to 20 miles and do this for both eclipses. This creates two different 40 mile wide observing zones for the two eclipses. We have to simulate the prime observing region by overlapping these two square observing zones centered at the intersection of the center lines. The area contained within both of the boxes provides the longest totality durations while observing both eclipses at “the cross” and this region of land now becomes less than 1,600 square miles. (Figure 3)
Figure 3. For eclipse observers who successfully witnessed the 2017 eclipse inside of the yellow box, they can try to witness the 2024 eclipse inside the red box to witness both at “the cross” and maximize their totality duration. (Boxes are approximately 40 miles square)
The precise intersection point of the two center lines varies slightly depending on the interactive map used to simulate the two eclipses. The point is southwest of Carbondale, Illinois, and appears to be located on private property slightly removed from the east side of the shoreline of Cedar Lake. At this point the maximum totality, duration for the eclipses could have been 2 minutes and 40 seconds in 2017 and could potentially be 4 minutes and 8 seconds in 2024. However, if located along the edges of the square boxes, the totality duration time would have decreased to approximately 2 minutes and 16 seconds in 2017 and should be approximately 3 minutes and 52 seconds in 2024.
Why are we so lucky and what caused “the cross?”
The fact that we can discuss this eclipse intersection, in some respects, is lucky because it has to do our present circumstances. We are simply the beneficiaries of two things: First, we just happen to live on the continent where the umbras will travel on the surface of the Earth. Second, we are alive at this point in time. We have these two eclipses because of the wonderful repeating clockwork of the solar system. This repeating clockwork concerning eclipses is called the saros. The term saros, from its ancient origins, describes a measure of time. When applied to our understanding of eclipses, the measure of time is 6,585.3211 days, which is called one saros cycle. The orbit of the Moon around the Earth has a complex gyration as both of them orbit the Sun and this gyration has a pattern that eventually repeats itself. So on a day when the Sun, Moon, and Earth are in an alignment that creates a total eclipse on Earth, a very similar total eclipse will be created 18 years, 11 days and 8 hours in the future. This is because the Moon and Earth have returned to the same orbital positions at the end of a saros cycle and they create a very similar eclipse path.
There are many saros series in progress at this time. The 2017 eclipse belongs to saros series 145. The 2024 eclipse belongs to saros series 139. The beautiful elongated paths of these eclipses have overlapped each other many times in the past and they will overlap each other many more times in the future. So “the cross” that we are enjoying was already enjoyed in Europe, across Turkey, in 1999 and 2006. (Figure 4)
Figure 4. Because of repeating saros cycles a similar cross of eclipse paths was enjoyed by Turkey in 1999 and 2006. Saros series 145 and 139, respectively.
There are two things that complicate any repeating saros cycle a bit more. The first is that the timing of the Moon and Earth gyration combined with the Earth’s rotation moves each subsequent eclipse path in a saros about 120 degrees to the West. That is why the same set of crossing eclipses that happened in Turkey now ends up in the U.S. (Figure 5). The second thing that varies in a repeating eclipse is the latitude changes slowly, moving southward or northward, depending on whether the eclipse occurs on an ascending or descending node of the Moon’s orbit. This is why a saros series eventually ends.
Figure 5. The two eclipse paths that cross in the U.S. These occur about 120 degrees to the West of the similar paths that occurred in Turkey in the past.
When these two eclipses move west again, in 2035 and 2042, observing them will be more difficult because the paths will cross over the Pacific Ocean (Figure 6).
Figure 6. Now located about 120 degrees to the west of the continental U.S., these two eclipses cross once again, but it occurs over the Pacific Ocean.
When a saros cycle repeats three times (54 years), the longitude progression has moved about 360 degrees, so the eclipse returns to the same region of the globe. In 2053, after three cycles, the eclipse of saros series 145 returns to the region of eastern Europe, but its latitude moves south. In 2078, after three cycles, the eclipse of saros series 139 returns to North America, but its latitude also moves south. Now that you understand the idea of the saros, you can appreciate that another eclipse chasing trivial pursuit is to observe different eclipses from the same saros series. You also realize to do this, because of the longitude shift, requires international travel. My first total eclipse was from saros series 127 on June 21, 2001, across Zambia, Africa. In 2019, I witnessed the eclipse in Argentina which was also from saros series 127. In 2024, when I observe the eclipse in the U.S., saros series 139, it is from the same saros series as the eclipse I witnessed on a ship in the Mediterranean Sea on March 29, 2006.
For additional stories about what the saros means to other eclipse chasers, I recommend this article by Jamie Carter found here.
What is your priority for 2024?
Although the discussion of observing the 2017 and 2024 eclipses in the region of “the cross” is technically interesting, remember that achieving this feat is secondary to seeing the total eclipse of the Sun and witnessing the corona. (Figure 7)
Figure 7. The spectacular 2017 corona as imaged from southeastern Tennessee. High dynamic range processing of four corona images and a fifth image for Moon glow.
The 2024 eclipse occurs on Monday, April 8. This is a time of year when no region of the country along the path is safe from bad weather. The future predictions for chances of clear skies for the 2024 eclipse put the best prospects in the Southwest and not at the point of “the cross.” And as you travel further to the northeast, the percent risk of cloud cover increases. (Figure 8)
Figure 8. Cloud cover risk prediction is incredibly helpful for eclipse planning. Jay Anderson, at the website Eclipsophile, is an expert at compiling and analyzing historical data. But on eclipse day in April, any place along the path in the U.S. could be at risk.
Carbondale has been advertising itself as the town in the path of both eclipses since well before the 2017 eclipse, and that’s fine because it is definitely exciting. And I am certain that the city leaders and the residents will do an excellent job preparing for and hosting the influx of eclipse observers who will come to their town (Figure 9). It will be similar to the success that Hopkinsville, Kentucky, had when they advertised themselves as the town that was Point of Greatest Eclipse for the 2017 eclipse.
Figure 9. The town of Carbondale, Illinois, certainly does have the distinction of being the major town in “the cross.” But you pick a final observing position for eclipse day based on the weather.
However, there is a YouTube video taken during the 2017 eclipse from Carbondale, at Salukis Stadium on the campus of Southern Illinois University, where thousands of people were gathered, but were clouded out and did not see totality. This was because that specific location had clouds in the sky in front of the eclipse right at the time of totality. So you must be mobile on eclipse day, even if it means moving just 10 or 20 miles for clear skies.
In 2017, I was corresponding with a lady from Missouri who lived in the path of totality and was excited about that and planned a big eclipse viewing party for family and friends in her backyard. Unfortunately, a large portion of Missouri had storms on eclipse day and this poor lady and her guests got completely clouded out.
Therefore, if you live in the path of the 2024 eclipse, that’s great, it can be your primary observing position, but you must have alternative observing positions. Please DO NOT plan a party at your house for eclipse day! Stay mobile on eclipse day. Plan your party for a couple of weeks later when you can share stories about your successful eclipse observations. (Figure 10)
Figure 10. The country had fairly good skies on eclipse day in 2017. The worst cloud cover was over northwestern Missouri, northeastern Kansas and eastern South Carolina.
Using the Solar Eclipse Timer app in 2024
Of course, the Solar Eclipse Timer app is ready to time the 2024 eclipse, but there are some interesting things to do before that. The formula to calculate the contact times is built into the app, the data set for the completed 2017 eclipse is still present and the data set for the 2024 eclipse is available. The app does not consider the calendar day, so all observing positions in the United States can be simulated for both eclipses. This is true whether you are in the path of totality or anywhere else in the country in the area of a partial eclipse. As you can see from Figure 11, the entirety of Canada and the U.S. fall within the penumbra, an area where some portion of a partial eclipse can be observed.
Figure 11. The huge limits of the penumbra also move across the U.S., providing the entire country with the ability to see some portion of a partial eclipse, with the exception of Hawaii.
So no matter where you live in the U.S., you can use your device to geolocate and see what your partial eclipse percent obscuration would be for both eclipses. Figure 12 shows the data if you were located at Kennedy Space Center in Florida, which is out of the path of totality for both eclipses.
Figure 12. The same observing position, Kennedy Space Center, has different maximum depths of the partial eclipse due to the difference in the distance away from the center line for the two eclipses. For 2017, maximum coverage gets to 86%. For 2024, maximum coverage gets to 56%.
If you happen to live in the path of the 2024 eclipse, you can geolocate and see what your contact times and totality duration will be. Remember, if you live in the path your residence can be your primary observing site, but you must plan for alternate sites to stay clear of clouds. When planning ahead for alternate observing sites in 2024, you can manually enter the coordinates into the app and calculate the contact times for a position and then save that alternate position for analysis or a site visit later.
Figure 13. The same observing position in “the cross” in Carbondale, Illinois, has different contact times and different totality durations due to the elements of the two eclipses.
So for the 2024 eclipse, if you are observing in “the cross,” make sure you load the correct eclipse data set on eclipse day! The data set for 2017 will still calculate contact times but they will be completely wrong!
Summary
This article presents the basis for understanding why the U.S. is in the path of two eclipses just seven years apart. If the subject of the Moon’s orbit, the saros and how a saros series progresses interests you, more technical explanations can be found in other resources. The 2024 eclipse presents wonderful opportunity to witness a total solar eclipse, without international travel, and I implore you to make all efforts necessary to get to the path!
Author bio
Dr. Gordon Telepun is a plastic surgeon who lives in Alabama. He is an expert eclipse photographer and eclipse educator. He is the developer of the mobile app Solar Eclipse Timer which is designed so he can be your personal guide and photography assistant through the stages of an eclipse. The app geolocates to calculate the precise contact times of an eclipse. It does audible countdowns to the contact times and max eclipse, announces when to observe for various partial phase phenomena and automatically calculates the clock times needed to achieve a perfect eclipse sequence image. It’s especially helpful for a total eclipse but it also has a partial eclipse timing mode.
Detailed eclipse educational videos can be found on his YouTube channel called Solar Eclipse Timer
Other eclipse information including details about the app is available on his website
Contact Dr. Telepun at: foxwoodastronomy@gmail.com
Report a Typo