Heavily amplified oxygen signal, projected back onto the 7772Å disk

With this new spectroheliograph, still in the tuning, I observed the infrared oxygen triplet at 7772, 7774 and 7775 Å, on 2025-12-13. As an ERF, I used a Nantong Foric bandpass filter, OD2-ish with the CWL close enough.

To the best of my knowledge, this is the first full solar disk with (amplified) oxygen features and prominences.

A subjective impression is that this oxygen line is somewhat similar to a weak helium. The line is in clear absorption on the disk, but turns into emission as going off the limb. Prominences are readily visible if bright, or become visible after applying math. Continuum subtraction shows that spots seem to be less dark, and the plages are also a bit shaded, less overall contrast.

Fe I 7781, used as a guide line for reconstruction

continuum taken from lambda 7773A

O I 7772

delta = oxygen – contiuum

delta sharpened

gong Ha for comparison

slit positions