I’ve been hunting oxygen smudges for a good while now, see here, here and here. But most if not all these smudges were close-ish to the equator. This one, on 2026-11-06 07:13Z showed up elsewhere. On the disk, at ρ 0.773R Ψ 209° corresponding to a solar latitude of ~38 degrees south.
This smudge has appeared at a relatively high latitude, compared to previous observations, with a rather unassuming hydrogen alpha footprint, with some smoldering at SDO AIA 304Å and 1600Å.
SHARD26 — the name the Atlas got. The collection of solar disks across the spectrum I’ve been amassing the past two years has more or less taken shape, with continuous coverage from near ultraviolet till as far as the CMOS is useful, deep into the near infrared, 355-1107 nm. Perhaps this name, perhaps with solar astronomy and spectrography added to the query, will be enough for search engines to lead curious people to where they wanted to get. So, here we go, SHARD26 – SpectroHeliography Atlas of Resolved Disks 2026. And a printscreen featuring the new title.
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.
I caught a disk center flare in O I 7772, nine scans centered around UT 2026-09-09 09:05. The signal on the disk below has been amplified through continuum subtraction etc, and an artificial flat corrects most artefacts, to highlight the oxygen features: darkened-mottled plages, darkened chromospheric network, dark flares, prominences and light blankets on and beyond the limb. A hint of a filament is visible here, though other datasets shows more obvious filaments.
For reference, a GONG frame
On 2026-09-20, I observed the Sun in O I 7772. I applied the same processing, applied an artificial flat to remove most artefacts. The two frames show considerable changes in the patterns shown by oxygen, while others rotate quietly together with the Sun.
The two frames are centered around UT 0800 and UT 1230, each frame is a stack of dozens of scans (around an hour).
As a bonus, the filament to the right of the disk center, is also obvious.
I used a modified Sol’Ex spectroheliograph, ML Astro Filter, EO 1800 gr/mm grating, and EO 775/25 OD4 bandpass filter, attached to a 72/430 refractor.
I observed the Sun in multiple wavelengths, Hα, He I 10830, O I 7772, and the disk center filament shows up rather obviously in the processed oxygen data.
I also tried hacking the Challenger Deep instrument, ultimately failing to improve its performance. The best addition proved to be yet another piece of black (both visually and IR) duct tape, covering a rogue area of the grating that’s perhaps rotated beyond its optimal angle.
O I 7772, false color, amplified via continuum subtraction, stack of data from multiple scans
O I 7772, amplified via continuum subtraction, stack of data from multiple scans
single scan Ha
single scan continuum around Ha
Previously, as described in Smudges in Oxygen, O I 7772 I hinted at the fact that smudges in oxygen are usually accompanied by bright smoldering in EUV, and that the difference between AIA 1600 / AIA 1700 is a potentially good indicator of where to expect smudges.
In 2029-09-15, I collected data where a prominent smudge appears in oxygen, without anything outstanding in other wavelength. The smudge persisted for several hours, during which the area in question didn’t flare.
The smudge is the dark „spot” at around 9 o’clock, corresponding to a plage and filament in Ha.
Stacking 12 scans, through continuum subtraction and further processing, I managed to reveal some really subtle details on the Sun, clearly showing filaments in Oxygen. Somewhat ironically, on this day, there were no flares, no smudges and no bright prominences, to add to the repertoire of the image presented here. I included AIA 1600, GONG and AIA/SUVI 304 for reference.
I consider it settled: there are filaments in oxygen, in O I 7772, on the disk of the Sun, and a Sol’Ex derivative amateur spectroheliograph can observe them.
Today I managed to gather the best data so far in support of having visible filaments in oxygen, over the solar disk. Nota bene, they have to be dark and dense filaments, as seen in hydrogen alpha, but they are there. A nice addition to the smudges.
I used the a customized SolEx spectroheliograph, with an 1800 ln/mm holographic grating, an EO in-cone prefilter centered to 775nm, ML Astro’s slit, and Altair Astro’s IMX 678M camera implementation. The assembly was mounted to a 72/430 doublet.
Because oxygen darkens over plages, filament observation is extra hard. But blink comparing against AIA 1600 and the iron from below the oxygen triplet reveals no candidate plages.
Ca II K, stack of 30 scans, centered around 2026-08-01, 0805Z
Ca II 8542, stack of 10 scans, centered around 2026-08-01, 0950Z
