Making carbon bright: dividing the disk edge frame with a nearby frame towards the disk center

With a spectroheliograph, I keep observing two carbon lines in the infrared, C I 9095 and 9112. Generally speaking, in both lines, the signal is weak. What I have seen so far: excess light over sunspots, a deficit of light over active regions, dark features that resemble the oxygen smudges and flares that look like darken on the disk.

While stray light could be the culprit for observing excess light in a dark line’s dark areas, as in light bleeds in, the deficit is another question, especially when it is visible against the continuum in blink compare, as a darkening, while the continuum shows no change. Then there are the disk edge phenomena, a surging-flaring prominence on 2026-07-05, at around 10:25UT, that are visible in the raw capture, without enhancement.

To enhance some frames, I decided to divide a frame close to the disk edge by a frame somewhat towards the disk center. Carbon, and only carbon, lights up. (tovább…)