Rule out residual flat-field systematics in the east–west asymmetry

Determine whether the observed east–west asymmetry and eastern color dependence of the F-corona are intrinsic or are caused by residual systematic errors in the stellar flat-field correction.

Background

The RAW analysis finds shallower eastern profiles than western profiles and a tentative wavelength-dependent eastern gradient. These effects persist across the two exposures, but the eastern profiles are particularly sensitive to the flat-field correction, and detector-fixed errors could reproduce the same pattern in both frames. Consequently, the intrinsic status of these asymmetries remains unresolved.

References

Ours is reproduced in the two frames, but because the eastern profiles are the most affected by the flat-field correction (Section~\ref{sec:decomposition}), a residual systematic error of the flat field cannot be excluded.

— Revisiting the Optical F-corona from the Artemis II Total Solar Eclipse with RAW Data: How Far Can Consumer JPEG Images Be Trusted for Astronomical Photometry?  (2610.20194 - Tsumura et al., 14 Oct 2026) in Section 4.1, “Radial Profiles” and Section 4.2, “Color Dependence”