One year until the 2020 Total Solar Eclipse - This eclipse is about symmetry and altitude!
This astronomy blog was written by Dr. Gordon Telepun, an expert eclipse photographer and eclipse educator with a special interest in the partial phase phenomena.
On December 14, 2020, South America will be in the path of another total solar eclipse. Similar to the 2019 path, the 2020 eclipse will reach the coast of Chile first and then cross Argentina.
The 2020 eclipse is beautiful due to its symmetry, but challenging due to its altitude.
The Symmetry of the Path
The entire path of the 2020 eclipse is a graceful long sweeping arc starting in the Pacific Ocean and ending in the Atlantic Ocean. The continent of South America basically splits the arc in half, although not quite at the point of the southernmost latitude of the path. The center of the path hits the coast of Chile at latitude -38.93° and exits the coast of Argentina at -41.16°. The southernmost point of the path is less than one degree more south at -42.04°. (Figure 1)
Figure 1. The Saros 142 eclipse path across the Earth is a beautiful and graceful arc with the continent of South America almost at its midpoint.
The symmetry of the path is made much more interesting because the Point of Greatest Eclipse is located in Argentina, almost in the center of the continent. Rough measurements along the path put the Point of Great Eclipse about 300 miles from the west coast in Chile, and about 245 miles from the east coast in Argentina. (Figure 2)
Figure 2. The Point of Greatest Eclipse is located in Argentina. Almost centered on the continent when measured from the points where the centerline intersects with the coasts.
The Point of Greatest Eclipse is a point on the surface of the Earth that is the result of the mathematical formula that calculates the circumstances of the path of the eclipse. When the center line of the umbra is extended into the Earth and it reaches its closest point to the center of the Earth at the Fundamental Plane, that center line creates the point that is transposed to the surface of the Earth. This is the Point of Great Eclipse. (Figure 3)
Figure 3. The Fundamental Plane is a plane that is perpendicular to the axis of the umbra. When the centerline of the umbra’s shadow is closest to the center of the Earth on the Fundamental Plane, that is the moment that creates the Point of Greatest Eclipse on the surface of the Earth.
Interesting symmetries happen around the Point of Greatest Eclipse and this is so well demonstrated with the 2020 eclipse since land-based observers will be in Chile and Argentina on this narrow portion of the South American continent. The totality duration at the Point of Greatest Eclipse is 2m 10s. The totality duration on the coast of Chile is 2m 8.4s. After traveling 545 miles east, to the coast of Argentina, the totality duration is 2m 8.9s. This is a difference of just 0.5 seconds over this distance of 545 miles.
My point is, 545 miles along an eclipse path usually would make a significant difference in totality time if this span of distance was to the east or the west of the Point of Greatest Eclipse. But when the 545 miles is split by the Point of Greatest Eclipse, there are symmetries on each side! (Figure 4)
Figure 4. Land-based observers in Chile and Argentina have similar totality durations due to the symmetry of the path.
For the 2020 eclipse path, the symmetry also occurs with the altitude of the eclipse at max eclipse. The Point of Greatest Eclipse being centered in the continent places the eclipse high in the sky throughout the path. Max eclipse occurs higher than 71° in the sky at all observing positions. (Figure 5 and Figure 6)
Figure 5. The highest altitude at max eclipse occurs at the Point of Great Eclipse. Because of the symmetry, the altitude at both coasts is almost the same.
Figure 6. The ecliptic of three observing position is overlaid. The sequence of the entire eclipse will be relatively horizontal. This eclipse is high in the sky making it difficult to frame the eclipse and the landscape together. CH – coast of Chile. GE – Point of Great Eclipse. AR – coast of Argentina. Simulations from Stellarium.
An extremely wide-angle lens is required to capture the eclipse and the horizon in the same frame when the eclipse is occurring at 71°. This has the disadvantage of making the size of the solar disk very small in the frame. Another technique would be to ignore the actual horizon, but in the foreground frame in a structure like a tree or interesting building which would allow a smaller field of view enabling a larger solar disk in the sequence.
The setting eclipse in 2019 provided a terrific opportunity to frame the eclipse and the horizon together. (Figure 7)
Figure 7. The 2019 eclipse sequence setting into the Andes mountains. This shot was possible because max eclipse occurred at 11.5°. In this picture 1st contact occurred at 23.6°. For the 2020 eclipse, max eclipse will be over 71°. So with respect to the horizon, max eclipse will be three times higher than the position of 1st contact shown in this image! But the sequence will be almost horizontal (See Figure 6)
Photography and Observing Considerations
A total eclipse occurring above 71° can be challenging to photograph and observe. If you are an astronomer/eclipse photographer and you will use a polar-aligned telescope, you will be able to point to 71° because this equipment is designed to do that. However, full testing of your set up before traveling is still advised. (Figure 8)
Figure 8. Polar aligned telescope mounts will enable pointing to 71°.
If you are a photographer relying on a tripod for camera support, you MUST test your gear before the eclipse! I own many camera tripods and I do not have one that can point to an angle of 71°! The upper leg mounting bracket and control arms interfere with obtaining this angle. The solution to this problem may be a high-quality ball mount on a sturdy tripod. But this is a less stable setup, especially with heavy camera gear. Testing your setup is crucial to confirm that you can point to over 71°. (Figure 9)
Figure 9. In my experience, very few camera tripods in their normal configuration can point to 71°. Some tripods can achieve a higher angle if the center post is elevated so control handles clear the base, but this sacrifices stability. The other option is a high-quality ball mount.
With either a telescope setup or a tripod setup having a digital camera with an articulating LCD screen is tremendously convenient. It is extremely difficult to work under your gear looking up at 71° through the standard camera viewfinder. If your camera does not have an articulating LCD screen you must consider purchasing a right angle viewing adapter. (Figure 10)
Figure 10. It is extremely difficult to use a standard camera viewfinder pointed upward at these angles. You will need either an articulated LCD screen or a right angle viewing adapter whether using a telescope mount or a camera tripod.
Using a right angle viewing adapter requires testing before the eclipse as it will alter manually focusing your camera. The right angle adapter will change the focusing of the system as seen by your eye. The procedure I use to set up a right angle adapter is as follows:
1. Using the automatic focus on the camera and a long focal length lens let the camera focus on something in the distance. Or use manual focusing indicators for something in the distance.
2. Now look through the camera viewfinder and adjust the diopter adjustment until the scene looks focused to your eye.
3. At this point tape down the diopter adjuster so it can’t move again.
4. Then attach the right angle adapter and adjust its focus ring until the same scene looks focused to your eye.
5. At this point tape down the focus ring of the right angle adapter so it can’t move again. Now you can trust doing manual focusing thought the right angle adapter, but only on the camera you worked with to set up the correct focus.
If you are an eclipse observer exclusively, you don’t worry about photographs, and you love the view of totality through binoculars, you must consider that it is uncomfortable and very difficult to hold binoculars steady when pointing up to 71°. You may consider using a monopod and a ball mount to help you steady the binoculars. (Figure 11)
Figure 11. Using binoculars to appreciate the corona requires a steady view. This is very hard to do when holding binoculars to look at this high altitude eclipse. A monopod can help you with this, but you must practice achieving this viewing angle before the eclipse.
If your primary eclipse enjoyment is using binoculars, you may consider viewing the eclipse by lying on the ground with something supporting your head or bringing a reclining lounge chair to help you comfortably point upward with more steady hands.
One Good Thing About a High Altitude Eclipse
Once you sort through all of the equipment issues, not everything about photographing a high altitude eclipse is bad. Depending on the conditions on eclipse day, you may have the advantage of better atmospheric clarity. Eclipses low on the horizon have more risk of having atmospheric conditions that can decrease the crispness of images of the corona. High eclipses like 2020, at over 71°, have a chance to have excellent atmospheric clarity allowing imaging the corona with more details.
This is apparent when comparing our totality images from 2017 in the U.S. and 2019 in Argentina. (Figure 12) These images were taken with the same telescope and motor drive mount, the same camera and the same techniques to achieve focus. Only the tripods were different. Each image combined 4 corona images and a moonglow image that was processed using the same techniques. So many of the variables that could affect the quality of images were controlled for. The improved details of the corona in the 2017 image can be attributed to in some part to the higher altitude of the eclipse and the better atmospheric clarity.
Figure 12. The 2017 corona image was taken when max eclipse occurred at an altitude of 63.4°. The 2019 corona image was taken when max eclipse occurred at an altitude of 11.5°. In 2020 max eclipse will occur at over 71° throughout the land path providing an opportunity to image the corona through excellent atmospheric clarity.
The 2020 eclipse crossing South America is very different than the 2019 eclipse which crossed South America. Its position on Earth and its graceful arc provides an opportunity to appreciate the symmetry of the central section of the path of an eclipse.
It presents some observation and photography challenges. Many of the tips and points discussed in this article will apply when preparing for the 2024 eclipse in the U.S., which has max eclipse occurring at 68° in southern Texas.
The Solar Eclipse Timer app is ready for timing the 2020 and the 2024 eclipses. A special feature of the app, which is available in the free section of the download, is the synchronized eclipse video practice session. This unique feature allows you to practice your photography and observation plan during the period around totality over and over with a few taps in the app. (Figure 13)
Figure 13. The Solar Eclipse Timer app is available for Apple and Android. It is also available in fully internationalized Spanish versions. It is a free download to try out.
Dr. Gordon Telepun is a plastic surgeon who lives in Alabama. He is an expert eclipse photographer and eclipse educator with a special interest in the partial phase phenomena. He is the developer of the mobile app Solar Eclipse Timer which is designed to be your personal guide and photography assistant through all stages of an eclipse.
An overview of his 2019 eclipse experience, including his research on the partial phase phenomena can be found by clicking here.
Other eclipse information including details about the app is available on his website.
Detailed eclipse educational videos can be found on his YouTube channel called Solar Eclipse TimerContact Dr. Telepun at email@example.comReport a Typo