Late June Sun

Solar Images 6 Days After the Solstice

It has been over a month since I last used my solar telescope! After many, many cloudy days an unusually clear, pleasantly cool morning arrived on June 26. The Sun displayed only one relatively unspectacular sunspot on this magnificent morning, but there was also a new emerging sunspot near the Sun's limb and a nice pair of prominences. First, check out the prominences:

(Click for full detail.)

On the other edge of the Sun, almost diagonally opposite the prominences shown above, was this nice scene:

(Click for full detail.)

Moving around the limb to the left from the image above revealed sunspot group 1513 emerging onto the Sun's Earth-facing side in this mosaic of 3 images:

Sunspot group 1513 is at upper left. (Click for full detail.)

The combination of my DMK41 camera, Lunt 100 mm H-alpha solar telescope, and 2X Barlow lens produces an image size roughly 10 arc minutes by 7 arc minutes. The Sun's apparent angular diameter is about 30 arc minutes. In order to capture the entire solar disk I would have to combine about 4 slightly overlapping images in width, and about 5 slightly overlapping images in height. These 20 individual images could then be combined in a mosaic showing the entire solar disk. If I could ever complete this monumental task, the result would be an enormous, detailed image, perhaps 4500 by 4500 pixels, showing sunspots, filaments, and prominences over the entire Sun.

The largest mosaic I've so far produced included only 9 images, less than half the number required for a full disk image. Here are some problems I encounter when trying to make a mosaic:

• Imprecise telescope mount movement is the biggest problem. The mount doesn't stop moving when I release the movement button. Instead, it continues temporarily drifting by unpredictable amounts. This makes it extremely difficult to cover the Sun with a precisely spaced patchwork of images.
• Varying brightness of individual images is another problem. All image brightnesses have to be manually adjusted so the combined mosaic is a smooth blend with no obvious brightness changes on the borderlines between constituent images.
• Image clarity varies across the mosaic if there is more atmospheric turbulence during one image than during another image.
• Finally, solar features continuously change. If too much time elapses while capturing the 20 images, they may not blend smoothly on the edges because edge features in one image have changed by the time the neighboring image is obtained.  

The first picture below is a mosaic of 4 individual images. It shows sunspot 1512 nearly centered on the lower portion of the Sun. Only this one sunspot group was prominently displayed on June 26. The field of view here is 20.2 arc minutes wide by 6.8 arc minutes high. Notice the imperfect brightness blending in the lower right:

Sunspot 1512 nearly centered (Click for full detail.)

 Let's zoom in for a closer look and move down a bit. We see sunspot 1512 above the lower limb:

(Click for full detail.)

Finally, here's a detailed single image of sunspot 1512 alone:

(Click for full detail.)

It was nice to observe on such a pleasant day! I only wish more interesting solar features were present.