FA-55729 / Astronomical coordinate conventions / Member archive

Celestial tangent projection: TAN detector latitude uses the longitude reference pixel · case 04

The adapter reports an incorrect pixel y while other fields remain valid.

Member previewVariant 4 · 3 implementations · 6 checks per implementation

Case contract

A supplied unnormalized direction basis has dot products east e, north n, and center z. The TAN chart accepts z>0 and returns e/z,n/z. Scale s and reference pixels rx,ry map this chart to detector pixels. Behind-plane rays are explicitly returned as None. Output fields are defined by: chart_east = d['e']/d['z'] if d['z']>0 else None; chart_north = d['n']/d['z'] if d['z']>0 else None; pixel_x = d['rx']+d['e']/d['z']/d['s'] if d['z']>0 else None; pixel_y = d['ry']+d['n']/d['z']/d['s'] if d['z']>0 else None; chart_valid = d['z']>0; reciprocal_center = 1/d['z'] if d['z']>0 else None

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	`{"chart_east": 1.25, "chart_north": 0.75, "chart_valid": true, "pixel_x": 10.625, "pixel_y": 10.375, "reciprocal_center": 0.25}`	`{"chart_east": 1.25, "chart_north": 0.75, "chart_valid": true, "pixel_x": 10.625, "pixel_y": 20.375, "reciprocal_center": 0.25}`	Failed

MEMBER ARCHIVE

The complete case is available to members.

This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

Member access is invitation-based. Sign in with your invited account to inspect the sources.