FA-55648 / Astronomical coordinate conventions / Member archive

Air vacuum line coordinate: Air-vacuum displacement is confused with the complete vacuum wavelength · case 03

The adapter reports an incorrect line displacement while other fields remain valid.

Member previewVariant 3 · 3 implementations · 6 checks per implementation

Case contract

The supplied index n=a/b is a positive rational greater than zero. This finite constant-index adapter maps air wavelength to vacuum by multiplication n. Frequency belongs to vacuum wavelength; flux densities change inversely with wavelength-bin Jacobian. It does not model dispersion of refractive index. Output fields are defined by: vacuum_wavelength = d['L']*d['a']/d['b']; air_wavelength = d['L']*d['b']/d['a']; vacuum_width = d['width']*d['a']/d['b']; vacuum_density = d['F']*d['b']/d['a']; vacuum_frequency = d['c']*d['b']/(d['L']*d['a']); line_displacement = d['L']*(d['a']-d['b'])/d['b']

Why this case matters

Catalog, detector, sky-coordinate, and spectroscopy adapters must preserve the association between numeric coordinates and their declared reference conventions.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
astronomical fixture 0	`{"air_wavelength": 8.0, "line_displacement": 18.0, "vacuum_density": 4.0, "vacuum_frequency": 6.666666666666667, "vacuum_wavelength": 18.0, "vacuum_width": 6.0}`	`{"air_wavelength": 8.0, "line_displacement": 6.0, "vacuum_density": 4.0, "vacuum_frequency": 6.666666666666667, "vacuum_wavelength": 18.0, "vacuum_width": 6.0}`	Failed

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