Meteorologists often fail to correctly forecast cloud cover. On August 25th one weather forecasting service predicted cloudy skies all day. Another forecasting service predicted completely clear skies and good seeing for a few hours after noon. The forecasts were contradictory! What actually happened?
The sky was almost completely clear around noon, giving me confidence in the reliability of the clear sky forecast. This temporary absence of clouds was the first opportunity in weeks to use my telescope. A few days before August 25th a relatively small sunspot evolved into a giant active complex feature. For days I watched it grow as it moved east to west across the Sun's face. Sunspot activity has been sparse lately, so this unusual episode of clear sky was an opportunity I didn't want to miss. If I didn't catch the sunspot this day, it would rotate out of sight before the next clear day. So I hustled and hauled my equipment outside. It takes about 45 minutes to set up the telescope, acquire the Sun, tune the solar filter, and get the computer and camera ready for imaging. During the setup time I'm usually looking at the equipment and not the sky. Consequently, I was shocked to discover thin clouds drifting across the first images on the computer screen. When I looked around the sky I saw massive cloud banks moving in from the north and west! The clouds had almost covered the sky in the 45 minutes it took to get my equipment ready!
I hurried to capture a few videos through cloud gaps before the situation became hopeless. Fortunately, a few images were relatively unaffected by clouds. The first picture below shows the large sunspot 2403 I had hoped to capture. (Click on the images for a larger view.) Some bright white energetic emissions appear in the space between the giant double umbra on the right and the four smaller trailing umbras on the left. There is good detail in the image, particularly the different shades of darkness in the four trailing umbras. This image was made with a 5X Barlow lens by stacking the 100 best frames from a 1000-frame video.
What a shame the clouds halted my session after less than an hour! The Sun had several nice filaments and prominences in addition to the large sunspot. I started capturing images for a whole disc mosaic, but had to stop after only nine panels were recorded. The next image is a 9-panel imperfect mosaic showing the immediate area around sunspot 2403. The Sun was in and out of clouds during the entire acquisition time.
No comments:
Post a Comment