Smudges in Oxygen, O I 7772 Csillagtúra

2026.03.07. 23:02:36

During my campaign to observe the neutral oxygen triplet in the infrared, through full disk spectroheliograms, I noticed a few things:

flares darken in oxygen, sometimes accompanied by shifts, one I measured was around 25 km/s
obvious doppler shifts (of at least 1 km/s) are rare, judging by a superficial inspection of my collected data
a general loss of contrast on the disk, active regions, plages darken and spots don’t darken that much,
dark smudges on the disk
chromosphere, prominences, some with doppler shifts,
a light blanket just beyond the limb, above the active regions, a feature I am familiar with from He I D3, He I 7065 and He I 10830
and a filament maybe (more on that later)

Smudges are areas that stand out as darker than expected, after taking into account spots, flares, and active regions. After contrasting the oxygen against a nearby continuum, either by subtraction or by division, smudges are revealed to be darker in oxygen, when compared to nearby active regions (which are themselves darkened) and thus a bit surprising. Smudges are stable across several minutes/hours, or even a day or two, while the flares I recorded are often times darker and short lived, on the order of minutes mostly. These smudges seem related to active regions, but don’t stand out in GONG Hα, where they can be a mere brighter spot like many others that don’t show up as smudges, nor AIA 1700 where the underlying area usually looks like any other active area that doesn’t show a smudge in oxygen. Better correlation can be seen with say SUVI 0304 or SUVI 0094 as small bright features in EUV, but it isn’t one-to-one either. Smudges stand out when they are somewhat towards the disk center, inside say 2/3 solar radii.

Below I compiled some scans with a nearby SUVI and AIA disk for comparison. I included smudges (marked with S), small and bright flares (marked with F), for context.

Instruments: 62/400 doublet, EO 775/25 OD4 narrow band filter, OD 0.6 neutral density filter, modified Sol’Ex, with 1800 ln/mm grating, modified/cooled ASI 678MM, JSol’Ex. Variable to good skies.