On 2026-10-19, I observed the Sun in the oxygen triplet, and processed data from O I 7772, using Fe I 7781 as the guide line to de-smile the spectrum. At around 09:00Z (12:00 Romanian time, UTC+3 at that moment), a flare showed up around the spots at four o’clock, bright in Ha (GONG) but dark, as usual, in oxygen. Subtle but obvious Doppler has also shown up in the triplet.

The oxygen reconstruction frame contains the counts from the O I 7772 line, raised to the power of 3. Thus limb darkening is exaggerated. The enhanced frames use the counts from the O I 7772 line together with subtracting the nearby continuum.

The before and during frames are each a stack of 8 and 9 scans respectively, thus a sum/average of about 10 minutes each. To remove instrument artefacts, and aid comparison between the two datasets, disk details were obtained against the artificial median/flat obtained from the stack, and these details were projected onto the same, artificially generated smooth disk, approximating the originals’ limb darkening.

Oxygen divided by a continuum, with Ha from GONG

blink compare

2026-10-19 0900Z gong, for reference

2026-10-19 0835Z, O I 7772 reconstruction before the flare

2026-10-19 0900Z, O I 7772 reconstruction with the flare

enhanced, before the flare

enhanced with flare

a slit position without (top) and then with the flare (second from top), and the difference between the two (bottom two renditions)

time lapse

reconstruction sample, 2026-10-19 0900, with a bird or an insect crossing while scanning