The Sun’s Aura – Solar Corona Revealed in All It’s Glory During Total Solar Eclipse 2024

Behind the Trip, from Portugal to Texas

Taking an high resolution HDR image like that represents an enormous amount of personal and professional efforts, as well as an incredible financial investment, and everything started many months before the Eclipse itself happened. Planning the trip to be on the right path, booking accommodation several months in advance, before prices went crazy, renting a car to be as much mobile as possible, and all of it without knowing if the weather will collaborate on the place we have choose to be for the special moment. Me and Apolónia, we travelled from Portugal to Pearsall, in Texas, as planned, but the forecast was indeed terrible almost in the entire US, or at least where the path was located. So after many hours driving from Dallas to Houston and then to Pearsall, with the rest of the week monitoring with several different models the evolution of the weather forecast, we have decided – even with a certain risk -that we must need to move back to north, again, to be more close to Oklahoma state. So on the day before the Eclipse, we had to drive back to Dallas during five or six hours and in the morning of the Eclipse, we did an extra two hours drive, to reach a small city called, Clarksville, in the northeast of Texas. At 10 AM the sky was still cloudy, and I only had 2 hours before the Eclipse starts, which means, to prepare my entire setup of 6 cameras with lens, tripods, mounts, filters, cables etc…. We found a nice green calm farm to setup everything. The owner kindly authorised us to stay with our car near by, thanks Ed. This was the most stressful time of our lives, without knowing until the very end, if we could make it, trying to focus and center the sun in between the clouds brought an extra difficulty to my task. Additionally, I only had 3 solar filters for 6 cameras. Fortunately, like a miracle, just 5 minutes before totality starts, the sky cleared up where the Sun was located and during the Maximum it was completely crystal clear, at least, for around 1min and 30 seconds, calm and windless until the end. It was just…Magical!!

Technical preparation and processing

My inspiration came from some of the most finest images I´ve seen so far, from pioneering Dr. Miloslav Druckmuller, and the incredible work of Nicolas Lefaudeux, as well as and the notable results achieved by my friend Petr Horalek. Just few months before the Eclipse I started going deep, researching and studying the processes involved in those kind of HDR Eclipse images. I red some of the papers by Dr. Miloslav, many other articles…and I knew it would be a very hard task. Specially some critical steps, as calibration and precise sub-pixel alignment in the linear stage, must be done using phase correlation, using correlated image structures to align them perfectly, which is done by non-available softwares, mainly developed by each of the authors, programmed and implemented themselves to apply the correct algorithm in a proper way. I don’t have access to a program with such capabilities and I didn’t wrote my own code – at least for now — so I had to find a different alternative for the critical steps. After many weeks testing and learning, I found the proper way to do it manually with pixel precision, using also calibration frames in the linear stage, but aligning and blending the seamless high dynamic range (HDR), free of artifact in the non-linear stage. There were helpful articles and tutorials along the way…from Fred Espenak, Alan’s Dyer (Books), Sean Walker (S&T article), and more recently by Bray Falls tutorial, but anyone was completely perfect on covering every aspects in case you plan to do both (Calibration, Aligning and HDR in Linear and non-linear stage). The image I’m presenting is the result of many hours of study and practice and a refined fusion of some of the techniques I’ve learned over the last years with some of you, so I’m thankful for that knowledge and want to show my deeply appreciation for that. I think that learning is the most beautiful thing, after…a Total Solar Eclipse :). With patience and knowledge, I tried to refine and improve some of the them, while integrating as part of my won developing workflow. It proved to be very efficient, as an example, after aligning all the brackets, and to achieve a perfect HDR merging while matching each exposure brightness levels, totally free of any artifact, I didn’t had to do, one single luminance mask during this non-linear stage, in order to get a well natural balanced light flow, ready for further enhancements of the corona details, such as removing the lowest spatial frequencies. It was incredible simple and it works like magic, I just need to check if also works so well on other different sets of Eclipse images, taken with different setups and exposures. Also important to say, specially nowadays, that this image, or part of it, was not AI generated, it’s of course, the result of a real hard amount of work captured and processed manually by myself. I’ve not even used during the processing stage, any AI fancy softwares, nor even to reduce noise, like Topaz. I used only PixInsight and Layering techniques in Photoshop.

The Sun’s Aura

The Corona is extremely hot and dynamic, being the outermost layer of the Sun’s atmosphere, it reveals intricate fine structures of delicate details distorted by the strong magnetic fields. Specially, close to the Solar maximum expected for 2025 (peak of 11 years cycle of activity), the plasma of the Sun’s corona features a lot of loops and wispy white streamers radiating into space. But due to an immense level of brightness it is only possible to see when the Moon is perfectly covering the Sun. Safe enough to enjoy with our naked-eyes, much more well prepared and efficient to comprise and accommodate a larger high dynamic range, than our cameras, which even nowadays can’t do it at once. This is why we need to cover around 14 stops in the dynamic range and probably even more would be best, but bracketing can help achieve this milestone.

And why is so special ? Because not even SOHO in space, from NASA, can watch the inner corona of the Sun in white light. It only can see the most extensive part of the outer corona, using a coronagraph, from two solar radii distant of the Sun’s centre.

Why Eclipse HDR is so Challenging

Photographing a Total Solar Eclipse, is probably to most advanced and complex task in all of astrophotography fields, not only from preparing and planning which requires a bit of Mat to find the correct set of exposures according to your gear combination, ISO, lens aperture, right place to be, right time to start etc, etc, as well as from executing it in a stressful short amount of time. But also very hard and difficult to process in a time consuming task. First, because the Sun, the Moon and the stars have all different motions across the sky, which are evident in long focal distances and long exposures. Images must be aligned not on the Moon’s disc, not on the stars, and not even on the prominences (as it only works in shorter exposures), so to reveal the corona in full glory, images must be aligned on the coronal structures which are very hard and tricky, as they are faint, subtle and lacking of contrast, and they keep moving too on a lower speed. Noticeable though over the course of all bracketing, but inevitably negligible, for the final fusion in order to naturally reduce the presence of noise. And probably the most difficult final achievement, is to keep as much as possible, everything looking natural without overcooking it. It is a delicate balance between, contrast, light flow, color and detail which I tried to keep in mind and respect until the very end. I hope I did it!

Equipment and Exposures

The High Resolution image was captured with a Sigma lens at 600mm at f6.3, and a Nikon D850 modified (Ha sensitive – not relevant for this type of TSE images) on a Vixen portable mount. I did more than 163 photos (bracketed exposures), but I’ve only selected 72 images (8 bracketed sequences of 9 shots each) to process, where the sky was crystal clear without any high cloud visible. The exposure time for each sequence bracketing was ranging from 1/125s, 1/60s, 1/30s, 1/15s, 1/8s, 1/4, 1/2s, 1s, 2s at ISO100, plus additional fast exposures of 1/4000 for C2 and C3 (Prominences and Baily’s Beads). 93GB of images were acquired just for this setup, being 1446 calibration frames such as flats, darks and bias (in a total of 65GB). Images used were captured during 1 minute and 28 seconds of the Maximum, during the 4 minutes and 19 seconds of Totality as seen from my location in Clarcksville, Texas.

Contacts C2 and C3

I merged the images from contact C2 and C3 in a single final photo, to reveal the best of all prominences visible around the Sun’s limb. This allowed to show the solar prominences and their associated magnetic loops on the final HDR image.

Moon Earthshine

Normally well seen one or two days after the new moon, the Earthshine phenomenon was described and drawn for the first time by the great Leonardo Da Vinci about 500 years ago on his book Codex Leicester, Leonardo da Vinci explained the phenomenon known as Earthshine in the early 16th century, when he realised that both Earth and the Moon reflect sunlight at the same time. Light is reflected from the Earth to the Moon and then back to the Earth as Earthshine. During Totality the Moon is in front of the Sun and can be seen in a long exposure. Indeed, it’s the only moment when is possible to capture the full disc of the Moon during New Moon phase. I was gladly surprised with the level of detail that could be seen, after a stack of the 0,5s, 1s and 2s exposures of all 8 bracketing combined together, comprising a total amount of 28s. The level of detail was then enhancement using a Local Histogram Equalisation with a large scale. Again, is interesting to show that a stack aligned on the moon, reveals the trails of background stars as the moon is moving much more faster then sidereal, and solar motion. Below: The image on the left, shows the natural Moon’s disc after the 28s stack, and before any further detail enhancement. Startrails are shown on the right image as the result of the stack.

Background stars up to 10.8 mag

The stack of the long exposures aligned on the stars, comprises a total amount of 28 seconds too, and can reveal stars down to magnitude 10.8. Interesting to note that the brightest star visible close to the left side of the Moon, – landscape version or upper in the portrait one – is indeed a variable double star in Pisces named: Zeta Piscium (86 Psc).

Coronal motion on finest structures

Loops in the inner corona are normally more slow and tend to not reveal obvious motion in such short amount of time (88 seconds), but streamers and small scale features seems to reveals some noticeable movement in the background. Some of the most interested features that my eyes could caught are highlighted with arrows at the lower left corner, showing what seems to be a displacement of a small scale structure. Besides the evident Moon’s motion, is also possible to notice some subtle radial motion on large scale features, visible in the background. Even not being as precise as sub-pixel phase correlation algorithm, the animation can also attest the high accuracy of manual alignment. Images used for this animation were acquired during 1 minute and 28 seconds of the Maximum during Totality in between 13h45m46s and13h47m14s Local time (-6 UT). Each successive 9 exposures set of images was aligned and processed independently to get 8 successive final composites of the solar corona. Then, the lowest spatial frequencies was removed and all composites were animated as a final Gif at a speed of 0,05 seconds each. Captured from Clarcksville, Texas, US, during Totality on April 8, 2024 with a 600mm lens f/6.3 on a Nikon D850. Note – you might feel seek if you focus your attention for a long period of time on the same spot. Make a few seconds pause, and then look back.

Acknowledgments

To produce a photo like that your investment may easily achieve the amount of a small entry level car, so fortunately, I had some extra support of some good friends that helped to make this possible. They know who are and their place in our thankful hearts. This image is dedicate to them, but specially to my dear girlfriend/wife Apolónia, as she not only planned every detail of the travel and ground trip alone when I was immersed in planning the technical stuffs, gears, cameras, lens etc…as she helped overcome all the single obstacles in our way that we faced since last year…and that, almost…made me give up of making this expensive trip to the 2024 Total Solar Eclipse. Last but not the least, to our lovely Sun, for being just mesmerisingly Beautiful and make it appear in between the clouds, for long enough, to make every drop of sweat count! To summarize the beauty of this event in a 1 minute video, I’ve created the Whispers of Totality.

Fine Art Prints – Available to ORDER

I hope you enjoy it as much as I do, and if you still want to support my work as an independent artist, you can buy this image as a Fine Art Print, a piece of Art to bring some magic to your sweet home! I will be deeply grateful for your kind support. I have created a special limited Edition of this Print supplied with a signed & numbered Certificate of Authenticity, global delivery with tracked & insured shipping, in a carbon neutral sustainable production, packaging and shipping. Explore the size options and prices by clicking on my Print gallery. Meanwhile, you can sign-up my newsletter to get early access of future Print releases.