Sunspots come and go, but some last longer than others. During my last imaging session on April 2nd a large active sunspot group near the Sun's western edge was about to rotate out of view. Apparently, some of this group kept active while rotating around the solar far side. On April 20th, a few days after reappearing on the Sun's Earth-facing side, the long-lived sunspots presented an interesting display. The next picture shows all the features in a single frame. (Click on all images for a more detailed view.)
From left to right are sunspots 2995, 2994, and 2993. Several nice prominences are located along the rim. A complex churning active area sits between three umbras on the right. There you can see white energetic patches together with darker filaments. This region had been the source of several major flares in recent days.
April 20th was a lovely day for imaging. Aside from a few contrails, the sky was completely clear, temperature stayed in the low 50's, and only gentle breezes blew. There was a chance I might be lucky enough to catch a flare eruption, so I took several images to see if anything was changing. In the next picture I centered the sunspots and processed the image to show sunspots but no prominences.
Notice the c-shaped filament on the left of the central sunspot group. As time went on this filament changed shape quite a bit. There were also a few minor energetic flareups among the white regions, but no major flares while I was watching. I made video clips once every minute for a bit more than an hour hoping to catch some activity that would show up in a time lapse movie. It takes quite a while to process more than 60 videos and assemble them into a movie. I'm still working on it.
It's difficult to display prominences in full detail without accompanying background noise. The next image is an alternate sunspot portrayal which shows more prominence structure than the first image above. Notice the hazy background brightness over the middle prominence. If I process the image to eliminate this haze, faint prominence structure also disappears. The dim haze wouldn't be so bothersome if it was uniform over the whole background. I still haven't figured out what causes the nonuniformity.
Sometimes, I try to manually erase background haze to make prominences look better. This is often unsatisfactory because some prominences then look unnatural. For example, look at the next animation showing a different portion of the solar rim than the images above. (I've blacked out the overexposed solar disc.) The animation switches between the unprocessed hazy background version and the manually erased background version. You can see how the largest prominence looks unnatural when I make the background dark.
Some really nice solar scenery was on display this day!
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