To Follow and Watch the Total Solar Eclipse in the USA

Shuang+PEI+Xin+RONG

The total solar eclipse is undoubtedly the most spectacular astronomical phenomenon in the world， and this miracle staged in the United States on August 21， 2017. For astronomers like us， following and observing total solar eclipse is like a pilgrimage. The ultimate purpose is nothing more than witnessing the wonderful moments that touch and move our spirit and soul. Since early August， astronomy enthusiasts from all over the world came to the United States. We are also part of those passionate "sun followers".

Reappearance of Total Solar Eclipse in the US in 100 Years

Solar eclipse falls into three categories， partial eclipse， solar eclipse and total solar eclipse. Among the various astronomical phenomena observable to mankind， total solar eclipse is one that is relatively hard to make a successful observation of. In terms of frequency of occurrence， the total solar eclipse is more likely to happen than the total lunar eclipse， but when there is a total lunar eclipse， half of the world in the nocturnal time can have a chance to see the full lunar eclipse， while the observation area of the total solar eclipse is extremely narrow， and often located in inaccessible areas like oceans and deserts. Normally total solar eclipse is far less frequently observed by people than the total lunar eclipse， unless all men hold the faith seek to follow total solar eclipse through the arduous journey.

When a total solar eclipse occurs， the shadow of the moon casts on the earth. Thus， a belt of shadow is formed， tens of kilometers to hundreds of kilometers in width. Only in this belt can we observe total solar eclipse. Its called total eclipse zone. In certain areas on both sides of the total eclipse zone， only partial eclipse can be observed. The total solar eclipse returns to the United States after 99 years. The total eclipse zone covers the area from Lincoln Beach in Oregon on the west coast of the United States to Charleston， South Carolina， going through 14 states in total. This is the first total solar eclipse observable only in the US ever since the founding of the United States in 1776， and is also the most widely and easily observed total solar eclipse. According to meteorological data over the past 22 years， the best observation sites for total solar eclipse are northern Oregon， Idaho， Wyoming and western Nebraska.

A Close Chasing After the Total Solar Eclipse

On the night of August 19， we finally entered the total eclipse zone at Riverton， Wyoming. On August 20， after careful selection， everyone finally chose a state park near the town as the observation point for total solar eclipse of the next day.endprint

Almost a whole night without sleep， on the next morning， we began to examine the satellite cloud image and the movement of the cloud up in the sky. Very unfortunately， somewhere near our observation spot， there was dark clouds gathering denser and denser. "Oh， the cloud may ruin our observation！" Said one of us. Now there were only 4 hours left for the total solar eclipse to take place. In order to ensure our successful observation of total solar eclipse， we made a provisional decision to drive to somewhere sunny and clear.

We therefore started our racing against time， "chasing the sun” crazily all the way. We finally arrived at Kasper City which lies 200 kilometers away after an hour or so， and that dark cloud was nowhere to be seen anymore. At this point， there was only 10 minutes left before the first contact. Thank God！

An Exciting Meeting with the “Dark Sun”

The whole process of total solar eclipse can be divided into five stages， namely， "the first contact – second contact - magnitude of eclipse - third contact – last contact." The stage of magnitude of eclipse marks the beginning of the total solar eclipse. The duration of this phase is related to the geographical location of the observation. We chose Casper because it is located right on the centerline of this total solar eclipse. The duration of the total solar eclipse was 2 minutes and 26 seconds.

First Contact

The first contact took place as soon as we were done with setting up our camera and other devices for observation. The very moment when the edge of the moon contacts the solar disk is called first contact. As the moon orbits the earth from west to east， the solar eclipse always starts from the west side of the sun.

Second Contact

The moment when the east edge of the moon cuts the east edge of the solar disk is known as second contact. Starting from this stage， we have entered the phase of total solar eclipse. The entire sun was obscured， and we felt the sky gradually dimmed， the temperature going down， with the autumn chill coming at an August noon. Before the start of the total eclipse， only rays of sunshine went through the rugged craters on the lunar surface， creating flickering spots on the edge of the sun. They are called Belle Beads.

With the disappearance of the last ray of sunshine， suddenly a circle of radiance burst out from around the sun. Cheer and scream of excitement broke out in the crowd. No words could describe the magnificent and fantastic moment. People usually deem the total solar eclipse to be daytime darkness， but only with the real experience of this whole process can you find that the sky does not actually darken completely， but somewhat similar to the evening twilight of the sunset. At this moment， we also saw a circle of pink glow around the sun， which is the sun's chromosphere. The spectacular prom， which is the red flame flickering around the sun， can also be observed in the active period of the sun.endprint

magnitude of eclipse

The moment when the central point of sun and moon overlap is called magnitude of eclipse. Only on the centerline of total eclipse zone can the complete overlapping of the center of sun and moon be observed； if not on the centerline but still in the total eclipse zone， the center point will be slightly deviated. In that case， we define magnitude of eclipse to be the point when the central points of the moon and sun are closet to each other. Normally we cant tell by the naked eye if it has entered the stage of magnitude of eclipse.

The point when the west edge of the moon cuts the west edge of the sun round is called third contact. Now the total solar eclipse was about to come to an end， and the sky was a little brighter than just some moments ago. Everyone was holding their breath， waiting for advent of the most gorgeous moment. Suddenly， bright splendor burst out on the edge of the sun， like a shiny diamond ring hanging on the skyline. This is called the diamond ring. With the forming of the diamond ring， another burst of cheering burst out in the crowd， and this marked the end of the most spectacular total solar eclipse.

Last Contact

Starting from the magnitude of eclipse， it seemed that the process of eclipse was going reversely， and the sun regained its radiance gradually. The splendor of the sun returned to the earth， the temperature increasing. As the last bit of gap the sun's edge was filled， the sun restored its roundness， which is called the last contact， and the solar eclipse was over.

Knowledge Link： The scientific value of total solar eclipse

The total solar eclipse is very important not only for its magnificence， but more importantly， it is because of the fact that scientists can conduct lots of researches and experiments with the total solar eclipse， including the studying and monitoring of the sun， as well as thermal radiation， electromagnetic radiation in different atmospheric altitude fluctuations. In addition， the influence of geomagnetic interference on biological action during total solar eclipse is also a very worthwhile research topic.

In the history of science， there have been many important astronomical and physical discoveries achieved with the advantage total solar eclipse. The most well-known example is the verification of Einstein's general theory of relativity through the total solar eclipse in 1919. In 1915， Einstein postulated the general theory of relativity， which was considered extremely difficult and implausible at that time. According to the prediction of this theory， the light would curve in a huge gravitational field. The strongest gravitational field accessible to human beings is the sun， but the light from the sun is so strong that it is impossible to detect whether the faint starlight from faraway would curve when it passed the sun， but with the total solar eclipse when the sunlight is blocked， detection on light curving becomes possible.endprint

Extended Reading： Do you wish to give it a try？

So far， I think some of you are getting excited about observing and taking pictures of the miraculous “Dark Sun”. From now on， lets look at some tips about the observation and photography of total solar eclipse.

1.How to observe total solar eclipse

Strong light may burn the eyes， so you can not directly observe with the naked eye. A Baader AstroSolar film glasses for observing total solar eclipse is alternative. If you are using a telescope， you will need a compatible Baader Astrosolar filter for your telescope.

2.The equipment needed for the photography of total solar eclipse

To take a close-up picture of the total solar eclipse， a telephoto lens not less than 400mm is required. If you want to take a picture of the total solar eclipse with landscape， you will also need to prepare a wide-angle lens and camera. The lens also needs to be equipped with a suitable Baader Astrosolar filter. Remote control shutter line is recommended for shooting the total solar eclipse. Just set the camera to automatic shooting mode， ang then you can enjoy the observation.

3. How to focus the sun accurately

There is also a small tip that helpful for taking a clearer picture of the sun. First， we switch the camera to manual focus mode， and then zoom in and observe the sun in the camera's LCD screen. If any sunspot is found on the sun， we then use them as a reference for manual focus until the sunspots become clear. This way we can have a much clearer photo of the sun than we do with autofocus.

Introduction of the Author：

Xin RONG， a natural photographer and traveler with rich experience on photography， whose photographic works won the silver medal of the photography contest on natural image held by the " Chinese National Geography " ， who has published several popular science books such as the Legend of Insects.

Shuang PEI， an environmental educator and popular science writer， who loves nature and specializes in the dissemination of astronomy and scientific knowledge.endprint