c01d3ec read OpenNGC's addendum, which brought in its only two DrkN rows, C099 the Coalsack and
B033 the Horsehead; NGC.csv has none. classifyOpenNgcType mapped DrkN to 'nebula', so both were
drawn as the backdrop's nebula sprite: ff86b0, additive, at the faintest opacity and the 70 pc
minimum size, about 1.6° across. The review measured it adding up to +59 in red over the Coalsack
beside Crux, where the sky has a dark hole, and darkening no pixel, as an additive sprite cannot.
DrkN is now among the codes dropped, with the reason beside the map. fetchDeepSky from cache keeps
488 objects against 490, still 107 Messier objects and every required id; README's count follows.
On :4302 the served backdrop holds 488 objects and the scene 488 sprites, neither of them C099 or
B033.
Control: DrkN mapped back to 'nebula' fails "leaves out a dark nebula, which a sprite that adds
light cannot draw" (1 of 801).
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
OpenNGC keeps the objects no NGC or IC number covers in a second file, addendum.csv, with the
same 32 semicolon-separated columns as NGC.csv. The ETL only ever fetched NGC.csv, so the
brightest deep-sky object in the sky, the Large Magellanic Cloud (V 0.29), was missing while
the Small one was drawn, and so were the Pleiades (M45), the Hyades, the Horsehead and the
Coalsack. fetchDeepSky now fetches the addendum beside NGC.csv, caches it as
openngc-addendum.csv, and runs its rows through the same loop.
Of its 64 rows, 27 pass the existing filters: all 22 named or Messier rows except M40, which
OpenNGC types as a double star, and M102, typed as a duplicate of M101; plus seven anonymous
open clusters brighter than V 9 (H05, H20, H21, Mel071, Mel101, Mel105, MWSC3171). deepsky.json
goes from 463 to 490 objects (galaxies 73 -> 85, clusters 294 -> 306, nebulae 96 -> 99), with
no existing record changed. Messier coverage goes from 106 to 107 of 110. 340 of the 490 have
a distance: the Pleiades 135.8 pc and the Coma Star Cluster 85.9 pc from their parallaxes;
the Hyades and the Local Group dwarfs honestly have none.
validateDeepSky now requires the Andromeda Galaxy and the Small Magellanic Cloud from NGC.csv,
the Large Magellanic Cloud and the Pleiades from the addendum, and at least 107 Messier
objects. Both checks were run against the real catalogue with the addendum removed: the ETL
fails on "Deep-sky object ESO056-115 is missing", and with the required list emptied, on
"Only 106 Messier objects were produced".
In the app, on the dev server: 490 sprites. The Pleiades sprite lies 0.00182 deg from Alcyone
(0.00183 deg from the published coordinates); the LMC 18.4209 deg from Canopus and 26.8215 deg
from Achernar (18.4209 and 26.8215 published); the Hyades 2.2591 deg from Aldebaran (2.2591).
The twelve labelled deep-sky objects now open with the Large Magellanic Cloud and the
Pleiades and include Brocchi's Cluster, in place of h Persei, chi Persei and NGC 2516.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
The design doc scopes deep-sky objects as a galaxy-view backdrop and lists
fetchDeepSky.ts, deepsky.json and deepsky.model.ts, but none of it existed —
it was the only part of the plan with no implementation behind it.
ETL: fetchDeepSky.ts pulls the OpenNGC catalog, classifies each object as a
galaxy/nebula/cluster, and keeps the ~460 worth drawing (everything Messier,
everything with a common name, and anything brighter than magnitude 9) out of
~12,000 mostly-anonymous rows. build.ts runs it and validates the output.
Distances are the hard part: OpenNGC has no distance column, and both fallbacks
fail for the best-known objects. M31, M33 and M42 are Local Group members whose
redshift is negative or absent, and a galaxy's catalog parallax comes from a
cross-matched foreground star — 6 mas for M31 would put a 780 kpc galaxy at
167 pc. So records store a unit direction on the celestial sphere rather than a
position (the line of sight is always known precisely, and the objects are drawn
on a fixed backdrop shell where true distance is unusable anyway), and distance
is optional metadata carrying its own provenance. Parallax is trusted only for
galactic objects, redshift only above z=0.003 where expansion outweighs peculiar
velocity. 330 of 463 get a distance; the rest honestly report none.
Rendering: DeepSkyRenderer paints the objects as soft additive billboards on a
2500 pc shell — clear of the 50 pc star field, beyond the camera's 2000 pc orbit
limit, and inside its 5000 pc far plane. Size comes from real angular extent, so
Andromeda is six times wider than the full Moon, clamped at both ends. Sprites
rather than points because the WebGPU backend caps point primitives at one pixel;
materials are shared per kind and brightness band, so 460 objects cost nine of
them. The brightest dozen get permanent labels, which needed the label overlay to
accept string ids alongside numeric star ids. The backdrop is decorative, so a
failure to load its dataset is logged and the star field comes up regardless.
Also documents the app in the README, which until now covered only the plugin
marketplace.
Tests: 112 passing, up from 54. Build, both typechecks and the Playwright suite
are green.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WaySiNst4HhDXBHnMy8p5G
SenrokaiandClaude Opus 5.5