This archive tracks four layers. A record present in 3 of them (HH, M41, IND) is silent in the rest, and says so.
The Horus HeresyM30–M31
imperium
Moon of Nocturne
An oversized moon locked to Nocturne, close enough that every fifteen years the two of them tear at each other. The XVIII Legion's armouries were up here, off the surface that keeps breaking.
Age of the ImperiumM32–M40
[RECORD LOST]
No record for this location in Age of the Imperium.
The 41st Millenniumpre-Rift
imperium
Salamanders fortress-monastery
The Chapter's actual home. Nocturne is where its people live; Prometheus is where the Chapter keeps itself.
Era Indomituspost-Rift
imperium
Salamanders fortress-monastery
Still in orbit, still forging, still the reason a Chapter that lost its primarch never lost its industry.
Position
Map frame: 628, 700 in the archive's 0–1000 disk space (core at 500, 500).
Distance from the core: 237 units ≈ 25.3k light years, south-east of the galactic core.
Height above the disk plane: 3.8 units — invented thin-disk jitter, deterministic per record. No published source gives any location a z coordinate.