# AT-HYG 3.3 classic-IDs derivative

AT-HYG by David Nash / Astronomy Nexus. [Pinned source](https://codeberg.org/astronexus/athyg/src/commit/fc08ca5a74ff6e595dab75a03a5ff3dc02b2793e). Data derivative: [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0/). Application code is separately licensed.

Raw/source/asset hashes, native units, bands, selectors and modifications are in manifest.json. The explicit HYG reference is checked against the separately pinned HYG 4.4 source; its metadata is not overlaid. The source subset uses HYG 4.2 lineage, so later labels/identifiers can differ. Complete link conflicts are in the hashed reconciliation asset. No NASA planet, private data or credentials are included; no deployment occurred.

Positions are source epoch/equinox 2000.0, with rounded source xyz and no supplied uncertainty. Missing source selector N/blank values are preserved. Tycho magnitudes/colors remain VT/BT-VT; other stated native values are V/B-V. Cartesian velocities are native km/s, including source-derived components with missing inputs; do not assume a measured complete velocity. Three finite source-selected distances exceed 100,000 pc; HYG's sentinel convention does not apply here. Sol remains ID 1 at the origin and is absent from background cells.