FA-55618 / Astronomical coordinate conventions / Member archive

Logarithmic spectral index: Log-grid channel widths are treated as globally constant · case 03

The adapter reports an incorrect channel width while other fields remain valid.

Member previewVariant 3 · 3 implementations · 6 checks per implementation

Case contract

A discrete logarithmic spectrum uses lambda(p)=L0*b**(p-r), b a positive integer >=2 and integer p,r. Redshift by a grid factor b**k is an additive pixel shift k. Coarse bin stride s changes the multiplicative channel ratio. Output fields are defined by: wavelength = d['L0']*d['b']**(d['p']-d['r']); next_wavelength = d['L0']*d['b']**(d['p']+1-d['r']); redshifted_pixel = d['p']+d['k']; rest_pixel = d['p']-d['k']; coarse_ratio = d['b']**d['s']; channel_width = d['L0']*d['b']**(d['p']-d['r'])*(d['b']-1)

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	`{"channel_width": 8, "coarse_ratio": 4, "next_wavelength": 256, "redshifted_pixel": 8, "rest_pixel": 4, "wavelength": 128}`	`{"channel_width": 128, "coarse_ratio": 4, "next_wavelength": 256, "redshifted_pixel": 8, "rest_pixel": 4, "wavelength": 128}`	Failed

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