Solar Processing Using Pixinsight

Solar Toolbox Process

While there are a number of different programs that can be used to process solar images, as a Pixinsight user, my favorite is the Solar Toolbox process by Bill Blanshan. This article takes us through solar processing from post-stacking to the final image.

The first steps are to open the image in Pixinsight and convert it from a mono image to one in RGB color. It will still appear gray, but we'll be able to add "artificial" color later.

Top image: the starting image after stacking 50 frames using AutoStakkert.

Bottom image: the final result after processing in Pixinsight.

Step 1: Adjust the Exposure

This will be a full-disc image featuring the solar surface and prominences, so we select that option under "image type".

We'll start by adjusting two of the three sliders. The blackpoint is fine, so we'll focus on the solar rim and the whitepoint.

Setting the solar rim value helps the toolbox find the sun's edge. Use the probe to find a reasonable K value for the rim. Here the value is 0.1339 so I'll start with that. Later tweaks by eye refined it to 0.15.

I started with a whitepoint of 0.9, but final tweaks moved it to 1.03, brightening up the center a bit.

I like inverted solar images because they display the details so clearly. I click the invert box, but that won't be visible on the sun's surface until the next step.

Step 2: Prominence Boost

We'll finalize the inverted look and bring out the faint proms using Prominence boost.

The amount parameter is pretty straightforward.

3d effect adjusts the shading of the solar disc to give it more depth.

Use highlight protection to ensure no whites are clipped.

Here you can see the full disc enhanced, with the surface inverted and the proms more visible.

The close-up shows the effect around this sunspot. Sunspots will appear white when using the inverted mode.

Step 3: Contrast Enhancement

Contrast enhancement provides a significant improvement. There are two types available. I usually prefer "local contrast", which is very easy to adjust. Don't overdo it-it doesn't take much.

The contrast mask is used to limit the effect to sun, thereby preventing contrast enhancement in the noisy background. I find it does a good job without any adjustment.

Step 4: Sharpening

This is my favorite step. The amount of detail that can be pulled out is remarkable. The "sharpen kernel" should be kept pretty low in a low-resolution image like this. "Sharpen boost" sets the amount of sharpening. It's easy to overdo this one.

Sharpening can also enhance noise, hence the denoise sliders.

Again, the mask limits the effect to certain areas of the sun and prevents us from sharpening noise in the background.

Step 5: Colorization

I typically add color in Photoshop, but the plugin can be used, as well.

Different colorizations can be made by adjusting the red, green, and blue sliders. Lower the blue slider to add yellow and move the green slider for fine adjustment to the overall red color.

The two contrast boost sliders work well.

At this point we'll apply the changes to the original image and close the Solar Toolbox.

Step 6: Curves

Final tweaks to the overall color balance, contrast, and saturation can be made using the Curves process.

Pull the curve up to enhance its characteristic and down to minimize it.

In this example, I've added red and a bit of green by pulling those curves up, and a bit of yellow by pulling the blue curve down (yellow is the opposite of blue).

The white curve adjusts overall brightness. I've darkened the darks by pulling the bottom of the curve down and enhanced contrast by pulling the top up, creating a steeper line. Steeper = more contrast.

Finally, we can enhance the overall saturation by pulling the purple saturation curve up.

We apply the process to the image once we're happy with our adjustments.

The Final Result

This close-up shows a yellow band around the sun's limb. This is a characteristic of an image created with a single-etalon scope. I can usually minimize it on one side of the sun but not the other.

See how I collected this solar data in the first place.

Google Sites

Report abuse