Magnetic Pinwheel

Worthy Sunspot Finally Appears

Solar activity continues to slide toward sunspot cycle minimum. For months now only modest, solitary sunspots have appeared. Finally, on April 10th, a good-sized sunspot, the largest of 2016 until then, came into good view. I decided to set up my telescope early in spite of the cold 40-degree temperature to take advantage of predicted good seeing. There was little wind, and no clouds, but seeing was not as good as predicted.

The first image below is a 6-panel mosaic showing solitary sunspot 2529 some distance from the eastern limb. The sunspot occupies center stage within a magnetic pinwheel of swirling gases. As you can see, no significant prominences or filaments were present in this quadrant of the Sun.

The sunspot umbra showed interesting structure. (Click on the image for a larger view.)

After capturing images in hydrogen-alpha, I dismounted my Lunt 100mm solar telescope and mounted a 130mm Stellarvue refractor. I hoped to image the sunspot in white light with new filters in place. A 1.8 neutral density filter and a uv/ir filter were installed in the light path. These filters attenuated sunlight enough so I could use suitable exposure times. The first white light image below shows decent detail in the sunspot umbra and penumbra, but surface granulation is washed out.

Many sunspot pictures I see online are processed to make the umbra completely black with no gradation of blackness. The next image is processed this way. It shows the granulation a little more clearly.

In the last two images I noticed how granules are smeared and indistinct in the upper left nearest to the solar limb. Apparently, this loss of detail near the limb happens in even the highest resolution images made by the orbiting Solar Dynamics Observatory, so this effect can't be caused by poor seeing or faulty image processing. The surface to the right of the sunspot shows evidence of granulation, particularly in the second image, but I'm disappointed in the lack of sharp detail. I think a combination of poor seeing and small image scale may be responsible for the blurry appearance .