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 to small to full cover the Sun. Eventually the observator 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 altumbra path, so I used a cameras located outside the main phenomenon in the area of partial eclipse. This observation was continued since last annular solar eclipse, which I was watching on 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 altumbra path in Chile.
My place of observation was “situated” on the Cerro Chapelco Base in the vicinity of San Martin de los Andes (Departament Lacar, Province Neuquen).
One camera is situated on the bottom the ski area and headed for south east, another two cameras record the image from the top and they are headed for north west. The image is reloaded for every 5 second.
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 occured around 13:30 UT with 81% obscuration (pic.3).
At the first glance picture no 3 looks a little bit darker than picture no 2, what 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 straightworward 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.
See the grass and the sky on the picture above (pic.4). Despite of the clouds, which briefly veiled the sun during the Ist contact (picture on the left) the grass looks more green than during the maximum phase, where it is mixed with green and quite strong yellow. When you see the sky the situation looks similairly, 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.
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 majority of outer parts of the Sun, when the brightest middle of the 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 another 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 wavelenghts dependence. Finally the shorter wavelenghts (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 wavelenghts are removed, thus we can see a little bit more long wavelenghts 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 exihbiting 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 sky just above the horizon. The camera situated in the valley is headed for south east (pic.4), so the sky is more 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 much higher part of 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 sky just above the horizon, hence the colour is brighter.
The last thing, which we can concern about is the brightnes 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 the 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 sun’s way across the sky. The camera is headed for south east. We need to know, that eclipse started during the morning, where sun was above south eastern horizon, so very close to the camera framing.
This observation was based on the Cerro Chapelco server, where are plenty of cameras deployed across the Cerro Chapelco Base ski resort.