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MkrGeo

An original point of view

Astronomy

The remote observation of partial solar eclipse

Partial solar eclipse 2017 in Argentina

Partial solar eclipse seen in north Argentina on 26.02.2017 (credits: Villa Gesell).

I would like to show my observation output. Last solar eclipse was visible throughout the southern part of South America in the morning and next in the western part of Africa during the evening. This eclipse was annular, so Moon’s disk was too small to fully cover the Sun. Eventually, the observer could see a beautiful ring. Traditionally it was possible to make a remote observation through the web cameras located in the area of the eclipse. Unfortunately, I couldn’t find a good camera in the antumbra path, so I used a camera located outside the main phenomenon in the area of the partial eclipse. This observation was continued since the last annular solar eclipse, which I was watching on the 1st of September. This time I focused on the sky. My point of observation was changes of the sky brightness during the partial eclipse. I took a very similar observation during the last annular eclipse, although the web cameras, through which I used to watch the scene were poor. In effect, I received quite small and pixilated images. I have learned from that time to use at least VGA cameras to do this kind of observations, thus I couldn’t use the cameras, which I found on the antumbra path in Chile.

My place of observation was “situated” on the Cerro Chapelco Base in the vicinity of San Martin de Los Andes (Department Lacar, Province Neuquen).

Chapelco webcams location

Pic.1 The web cameras based on the Cerro Chapelco Base. Number 1 – camera headed for the south-east, number 2 – 2 cameras headed for the north-west.

One camera is situated on the bottom of the ski area and headed for the south-east, another two cameras record the image from the top and they are headed for the north-west. The image is reloaded for every 5 seconds.

The first contact was around 12:20 UT. I started my observation at 12:15 UT (pic.2) and finished at 13:45 UT. The maximum eclipse occurred around 13:30 UT with 81% obscuration (pic.3).

Partial solar eclipse 2017 Cerro Chapelco webcam results

Pic. 2 A first photo pack from my observation (just before Ist contact): left – cameras situated on the top, headed for north-west, right – camera situated in the valley, headed for the south-east.

Partial solar eclipse 2017 Cerro Chapelco webcam results from greatest phase

Pic. 3 Photo pack from the maximum eclipse at 13:30 UT: left – cameras situated on the top, headed for north-west, right – camera situated in the valley, headed for south-east (chapelco.com).

At the first glance picture, no 3 looks a little bit darker than picture no 2, which is understandable. However is one important thing, which may bother eagle-eyed observators. If you look exactly on the sky during the greatest eclipse you can guess that this blue colour isn’t blue like it was during the Ist contact. To be straightforward during the partial solar eclipse sky should get darker in the same colour, but images (pic.3,4,5) shows, that this blue colour contains some red colour influence.

Partial solar eclipse 2017 Cerro Chapelco base Argentina webcam image comparison

Pic. 4 The comparison of the images from a camera situated on the valley: left – Ist contact, right – greatest eclipse (chapelco.com).

See the grass and the sky on the picture above (Pic.4). Despite the clouds, which briefly veiled the sun during the Ist contact (picture on the left) the grass looks greener than during the maximum phase, where it is mixed with green and quite strong yellow. When you see the sky the situation looks similarly, the sky during the Ist contact is light blue (only blue possibly with a little bit part of green). The sky captured around the greatest eclipse is dark blue with red colour influence.

Partial solar eclipse 2017 Cerro Chapelco base Argentina webcam image comparison 2

Pic. 5 The comparison of the images from the camera situated on the hillside: left – Ist contact, right – greatest eclipse (chapelco.com).

The explanation for this may be the colour of solar disk. Basically, the outer parts of solar disk are a little bit redder. During the deep partial solar eclipses, we can see the majority of outer parts of the Sun, when the brightest middle of our mother star is covered by the Moon. It may explain why we are witnessing this situation always when the obscuration is higher than 50%. I can’t say for sure, that this issue causes the red light appearance, possibly there are other reasons e.g. Rayleigh light scattering. Rayleigh scattering makes sky blue during the day when the Sun is high above the horizon and exist a strong wavelength dependence. Finally, the shorter wavelengths (blue) scatter more than longer (yellow and red). During the partial solar eclipse, where most of the Sun’s disk is covered by moon some of the wavelengths are removed, thus we can see a little bit more long wavelengths in the atmosphere.

We need to keep doing the observations like this (don’t ignore the partial eclipse phenomenon) to gather more proves and data to make a final conclusion.

The picture no 5 not exhibiting this effect. The scene during the greatest eclipse (on the right) is notably darker than during the Ist contact in the morning (left side). Basically, the direct sunlight during the maximum phase is just a little bit brighter than a shadow of clouds just before the eclipse.

Another notable issue is the colour of the sky just above the horizon. The camera situated in the valley is headed for south-east (pic. 4), so the sky is darker above the horizon because the path of annularity was coming south of the observation place. On top of that, the bottom camera could not frame a much higher part of the sky due to the high mountains. Unlike to camera situated on the valley, the camera from the top was able to image the lower part of the sky just above the horizon, hence the colour is brighter.

The last thing, which we can concern about is the brightness asymmetry caused by the ISO sensitivity in the cameras. As you see below (pic.7) the pictures started getting brighter just after the greatest eclipse. I mentioned this topic during the African eclipse. Unfortunately, not every camera could give me a clear observation output. In order to the camera situated in the valley (pic.6) is really hard to notice, when the eclipse exactly happened. There are two reasons, which made this situation so difficult: the clouds, which sometimes covered the sun and the sun’s way across the sky. The camera is headed for the south-east. We need to know, that eclipse started during the morning, where the sun was above the southeastern horizon, so very close to the camera framing.

Partial solar eclipse 2017 at the Cerro Chapelco base through webcam, results

Pic. 6 The observation output from the camera situated in the valley (Chapelco.com).

Partial solar eclipse 2017 at the Cerro Chapelco base through webcam, results 2

Pic.7 The observation output from the camera situated at the top of the hillside (Chapelco.com).

This observation was based on the Cerro Chapelco server, where are plenty of cameras deployed across the  Cerro Chapelco Base ski resort.

Mariusz Krukar

Links:

Amazing photos from the annular eclipse in Chile (German)

Detailed photos from the annular solar eclipse above Argentina (German)

The live stream observation of the “African ring of fire”

Spaceweather Eclipse Gallery

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2 Comments

  1. Eclipse

    This is caused by light scattering (mostly Rayleigh) because the Moon blocks the Sun partially, similar to what you can get at sunrise or sunset but less pronounced.

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