The Sun on July 3, 2024

Out here on the West Coast, we’re due for a significant warmup over the next several days. This morning, I thought it would be a good day to have a look—a safe look, of course—at the source of all that heat.

Here’s what the view looked like through my double-stacked 60mm H-alpha Lunt solar telescope:

To make this image, I performed my usual postproduction edits to white balance, gamma input levels, sharpness, contrast, and shadow and highlight brightness.

With some prompting from an article by Chris Schur entitled “Solar Image Processing,” which appears in this month’s issue of Sky and Telescope, I decided to make some additional changes in the tone curve adjustment pane in Canon’s Digital Photo Professional.

First, I selected the red channel and adjusted the input level to range from 40 to 255. This cut some of glare around the outer edge of the solar disk. Next, I selected the blue channel and adjusted the input level to range from 180 to 255. This eliminated much of the harsh magenta tone that has characterized most of my H-alpha solar imaging, and it rendered the Sun with a more pleasing orange color. I played around with the green channel but decided to leave it alone.

Incidentally, I was surprised to see any data turning up in both the green and blue channels. Theoretically at least, the problem with using a conventional digital camera with a dedicated H-alpha solar telescope is that, together, the etalon and blocking filter will only allow through an impossibly narrow sliver of light located squarely in the red region of the spectrum around 656 nm. (This article on Sky and Telescope’s website explains H-alpha solar observing in far more detail.) Since most digital cameras have a Bayer color filter array, only a quarter of the sensor’s pixels should detect red light, and image resolution takes a hit as a result. Why data is turning up in the green and blue color channels is a question I don’t have an answer for.

Anyway, here’s the end product:

I liked what those additional tone curve changes did to my image, and I think I may follow this approach moving forward.

That impressive prominence off the lower left looks like it’s leaning toward what appears to be a disconnected mass of plasma floating off the edge of the Sun. In fact, those two objects are part of a single mass that turns up far better as rendered at 304 Å by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory:

My little Earth-bound solar scope can only see so much. Usually it can pick up only the brightest prominences. To see more, it always helps to have a telescope sitting out there in space.

For good measure, I also took this photo of the Sun in white light using my trusty Orion 4" Maksutov-Cassegrain telescope equipped with a glass white-light filter:

In recent days, I’ve been keeping an eye on current solar activity, and I’ve been seeing some nice action in the chromosphere and photosphere. In typical form, however, it’s taken me a few days to get my solar observing gear out in the backyard. I think I may have missed the best views—the most active areas appear to be rotating out of view.