Solar Photography

by Kevin Shank | Jul 1, 2024 | 0 comments

The aurora superstorm in May has captured my attention—not just the beauty of the aurora, but the beauty of the sun from which the storm originated. There is an incredible photo of the sun on page 2. Just how did Mr. Schumann capture that exquisite detail!?

All solar photography that captures the surface texture of the sun is done through a filter other than a “white light” filter. Some photography is done in the ultraviolet wavelengths. Probably most backyard photographers who photograph the sun apart from a white light filter are using a solar telescope that has hydrogen alpha filtration.

To capture the greatest detail, a monochrome camera is used. Many photos are taken, from which a percentage is used to stack into one photograph. False color is then applied to colorize the photo, making it more fun to view and more realistic.

Colorizing a grayscale photo has been a challenge for me. Recently I learned a new technique that has significantly improved my results, and I want to share that process with you.

But first, I’ll give a very brief overview of the workflow capturing the data to begin with. We use an 80mm dual etalon solar telescope. Attached to the telescope is a ZWO ASI174MM camera. It inserts into the eyepiece focuser in lieu of the eyepiece. The camera is connected to a computer using a USB cable. As we watched the sun on the computer monitor, we tweaked the pressure tuner on the scope to alter the amount of air pressing on glass elements inside of the scope. By tuning in this way, we can more accurately achieve the sharpest detail on the surface.

We used SharpCap software to capture the data. Settings included 8-bit fits files, zero gain, and whatever milisecond exposure was needed to properly expose the shot. We then set the software to capture 4000 photos. Once the photos were captured, I used AutoStakkart to combine 30% of the best photos into one for the picture you see here.

In Photoshop, detail was brought out by adjusting the RAW file. Primarily I use the clarity, dehaze, and sharpen sliders, but also make other adjustments as needed.

To colorize, begin with the file in grayscale and 8-bit. Under the mode tab, switch to “duotone.” In the duotone options, choose quadtone. I am using black, yellow, and two shades of orange as my four colors.

To further customize where the various colors show up on the photo, use the curves slider to move the line up/down as shown in the screenshot.

screenshot of colorizing sun photo

The yellow slider is the color that is expanded in the curve menu. Notice how you can select points along the curve line to raise/lower them. Also notice the grayscale bar at the bottom. The white point is far left and the black point is far right. The curve line adjustments correspond with the grayscale. This curve provides a lot of yellow in the light tones of the map. Compare that to the curve beside the black color which shows very little black in the light tones. (See small curve graph left of black color swatch.)

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