observatory.nvim 🌃

A huge collection of space related colorschemes, all on a true black background, each one's palette derived from an emission spectrum, a blackbody temperature, a planetary albedo, a light curve, a color index, a photographic characteristic curve, or an optimiser.

Note

All color palettes where selected, measured and computed carefully by Opus 5, each one having its own constraints. See the head comments in each palette for more info.

Table of Contents

• 🌠 Features
• 🔨 Installation
• ⚙️ Options
  • 🛞 Overrides
  • 🖥️ Terminal colors
  • 🔩 Integrations
• 🎨 Colorschemes
  • Sky
  • Solar system
  • Stars
  • Exoplanets
  • Nebulae
  • Galaxies and deep fields
  • Events
  • Readings
  • Constructions
• 📓 Recipes
• 📜 License

🌠 Features

• 150+ colorschemes.
• #000000 background (optional transparency).
• Opt-in integrations with 27+ plugins.
• Optional terminal colors supporting 3 modes.
• A detailed and structured index for colorscheme filtering.

🔨 Installation

Requires Neovim >= 0.9 and a true-color terminal.

{
  "moyiz/observatory.nvim",
  lazy = false,
  priority = 1000,
  config = function()
    vim.cmd.colorscheme "observatory-milkyway"
  end,
}

With options:

{
  "moyiz/observatory.nvim",
  lazy = false,
  priority = 1000,
  opts = {
    transparent = true,
    terminal_colors = "diagnostic",
  },
  config = function(_, opts)
    require("observatory").setup(opts)
    vim.cmd.colorscheme "observatory-crab"
  end,
}

⚙️ Options

require("observatory").setup {
  transparent = false,      -- clear the editor background
  italic = true,            -- comments and builtins
  bold = true,              -- keywords, functions, titles
  undercurl = true,         -- diagnostics and spelling; off means underline
  terminal_colors = false,  -- true | "nearest" | "diagnostic" | "synth"
  integrations = {},        -- opt in per plugin, e.g. { telescope = true }
  overrides = {},           -- highlight groups of your own, keyed by scheme
}

🛞 Overrides

Highlight groups of your own, keyed by the scheme they apply to:

require("observatory").setup {
  overrides = {
    ["*"] = { Comment = { italic = false } },
    ["observatory-plate"] = function(c)
      return { ["@keyword"] = { fg = c.text, bold = true }, WinBar = { link = "StatusLine" } }
    end,
  },
}

"*" is every scheme and is applied first, so a per-scheme tweak layers on a shared one. A value can be a function of the palette, which is how to write an override against the scheme's own colors instead of a hex literal. It is the palette keyed by role - bg, text, comment, kw, str, func and so on - and require("observatory").palette() returns the same table for use elsewhere.

A spec is merged into the scheme's own, so naming one attribute keeps the color the palette chose - { italic = false } above leaves Comment the color it was. A spec that links replaces outright, since nvim_set_hl ignores everything else once link is present.

Overrides are applied in the same pass as the rest of the scheme rather than from an autocmd on ColorScheme, which matters in three ways: they take effect when you set them, even if the scheme was already loaded before your config ran; they do not compete for ordering with the other plugins listening to that event; and require("observatory").groups() reports what is actually on screen.

🖥️ Terminal colors

This plugins supports setting vim.g.terminal_color_0 through 15 for :terminal buffers.

Off by default. When you turn it on, the question is what to do about missing colorscheme colors.

Method	Description
"nearest"	Never invents a color. Uses the closest one the scheme owns (default).
"diagnostic"	Red, yellow and green come from the scheme's own error, warning and git colors. Others come from the nearest accent within 40 degrees, or are built.
"synth"	Builds all six at canonical hues, using the scheme's own mean saturation and a contrast its ladder already uses.

For schemes that have no hue:

• "nearest" takes red, yellow and green from the diagnostic colors and collapses others onto them.
• "synth" builds all six at canonical hues on a saturation ladder of zero, so they come out as six barely tinted grays. Both are the right answer for a palette that never contained those colors.

🔩 Integrations

Opt-in.

Plugins mostly declare their groups with hi default link onto core groups. Each integration covers the remainder - hardcoded colors, missing links or links I disagree with.

Available integrations

• aerial
• blink
• cmp
• dap
• diffview
• flash
• gitsigns
• illuminate
• indent_blankline
• lazy
• mason
• mini
• navic
• neo_tree
• noice
• notify
• nvim_tree
• rainbow_delimiters
• render_markdown
• snacks
• telescope
• todo_comments
• treesitter_context
• trouble
• which_key
• window_picker

🎨 Colorschemes

158 schemes in 9 families, 75 sampled from an image, 77 computed from a measurement and 6 solved for separation alone. Their floors run 8.1 to 30.4 ΔE.

from is where the colors came from: an image, a measured quantity, or solved for separation alone. ΔE is the closest pair of colors that can appear adjacent -- higher is easier to read. hue is the width in degrees of the band the accents occupy, so a small number means a near-monochrome. n is how many distinct accents carry the ten syntax roles; fewer means roles deliberately share.

Browse the whole collection.

Sky

Things that happen in Earth's own sky, none of which hold still long enough to be photographed the way a planet is. Most convert emission lines to hues; three of them convert a diffraction pattern, a temperature, and the path a sunbeam took through the atmosphere.

Scheme		from	ΔE	n	hue
observatory-aurora	the green aurora, on its own night sky	measured	12.5	9	200
observatory-aurora-red	the rare all-red aurora, green demoted to an accent	measured	12.0	8	232
observatory-comet	two tails, two hue families, nothing in between	measured	10.7	7	197
observatory-eclipse	the corona, almost colorless, with one ruby line	measured	11.4	8	194
observatory-hubble	the Hubble palette, which lands on the corners of the RGB cube	measured	13.5	8	300
observatory-nacreous	iridescent ice at 20 km, and the only pastel here	measured	12.4	6	229
observatory-nightsky	star colors by spectral class, on a deep blue sky	measured	10.7	7	170
observatory-noctilucent	sunlight that has already gone below the horizon, seen from 83 km	measured	21.3	6	204

Gallery

observatory-aurora	observatory-aurora-red
observatory-comet	observatory-eclipse
observatory-hubble	observatory-nacreous
observatory-nightsky	observatory-noctilucent

Solar system

Eight planets, nine moons, two dwarf planets, one contact binary and one ring system, each sampled from the portrait its mission is known for, and most of them paired with the reflectance spectra that portrait is a picture of. Half the solar system is a shade of tan and the palettes say so; four worlds photograph with no color at all, and their faint warm-cool split is amplified rather than replaced with a hue they do not have.

Scheme		from	ΔE	n	hue
observatory-mercury	the enhanced-color globe: tan crust, blue minerals, gold plains	image	9.5	8	234
observatory-mercury-computed	the grayest planet, mapped by reflectance unit	measured	11.3	8	197
observatory-venus	cream cloud in every direction, and nothing else	image	10.1	4	170
observatory-venus-computed	the cloud deck above, the surface nobody sees below	measured	15.5	8	143
observatory-earth	ocean, vegetation, desert, ice	image	9.6	6	182
observatory-earth-computed	the only world that needs no help finding colors	measured	11.6	9	196
observatory-luna	the full moon: five grays and a warm cast	image	11.1	4	60
observatory-luna-computed	gray, until you stretch it	measured	12.0	8	198
observatory-mars	rust, dust and one bright polar cap	image	16.5	5	177
observatory-mars-computed	rust, with the blue its sunsets actually are	measured	14.4	8	205
observatory-jupiter	zones, belts and the Great Red Spot	image	17.3	5	185
observatory-jupiter-computed	zones, belts, the red spot and the blue poles	measured	12.0	8	186
observatory-io	sulfur, ochre and frost, and no blue anywhere	image	17.7	6	18
observatory-io-computed	sulfur yellow, with frost as the only cool thing on it	measured	11.5	7	193
observatory-europa	ice, and the rust-brown cracks across it	image	17.2	5	44
observatory-europa-computed	water ice, and whatever the ocean brought up	measured	11.0	8	194
observatory-ganymede	grooved terrain in tan, and the frost at its poles	image	16.7	4	16
observatory-ganymede-computed	grooved ice over ancient rock	measured	14.3	8	190
observatory-callisto	the most cratered surface known, in dark tan	image	18.5	6	156
observatory-callisto-computed	the oldest surface, and the least to say about it	measured	17.5	6	188
observatory-saturn	pale gold, with the rings' shadow laid across it	image	17.2	4	12
observatory-saturn-computed	butterscotch, with the blue winter hemisphere	measured	11.8	8	196
observatory-titan	a hazy orange orb, which is all anyone sees from outside	image	16.9	4	142
observatory-titan-computed	an orange monochrome; the haze admits nothing else	measured	10.7	7	31
observatory-enceladus	white ice, and the fractures that vent it	image	11.6	4	195
observatory-enceladus-computed	the brightest surface in the solar system	measured	14.1	8	28
observatory-iapetus	two-tone: snow on one face, tar on the other	image	17.1	6	141
observatory-iapetus-computed	two hemispheres, and nothing in between	measured	15.2	7	198
observatory-uranus	featureless pale cyan, and that is the observation	image	16.2	4	40
observatory-uranus-computed	the most featureless palette here, and honestly so	measured	13.2	7	14
observatory-neptune	azure, a shade deeper than Uranus and no bluer	image	10.4	4	3
observatory-neptune-computed	the iconic blue, which is not quite the real one	measured	11.4	8	54
observatory-triton	cantaloupe terrain under a pink nitrogen cap	image	8.5	4	169
observatory-triton-computed	cantaloupe terrain and pink nitrogen frost	measured	12.9	8	176
observatory-pluto	the heart, in cream and tholin tan	image	18.1	4	4
observatory-pluto-computed	nitrogen ice, tholin red, and a blue sky	measured	16.2	8	192
observatory-charon	gray ice, and one red-brown pole	image	9.8	5	162
observatory-charon-computed	Pluto's tholins, arrived second-hand	measured	14.7	8	190
observatory-ceres	blue-gray regolith around one bright crater	image	15.8	4	130
observatory-ceres-computed	bright salt on a very dark world	measured	18.0	8	196
observatory-rings	a scan across the annuli, unlit side	image	18.2	4	127
observatory-arrokoth	the reddest thing photographed up close	image	8.1	4	3

Gallery

observatory-mercury	observatory-mercury-computed
observatory-venus	observatory-venus-computed
observatory-earth	observatory-earth-computed
observatory-luna	observatory-luna-computed
observatory-mars	observatory-mars-computed
observatory-jupiter	observatory-jupiter-computed
observatory-io	observatory-io-computed
observatory-europa	observatory-europa-computed
observatory-ganymede	observatory-ganymede-computed
observatory-callisto	observatory-callisto-computed
observatory-saturn	observatory-saturn-computed
observatory-titan	observatory-titan-computed
observatory-enceladus	observatory-enceladus-computed
observatory-iapetus	observatory-iapetus-computed
observatory-uranus	observatory-uranus-computed
observatory-neptune	observatory-neptune-computed
observatory-triton	observatory-triton-computed
observatory-pluto	observatory-pluto-computed
observatory-charon	observatory-charon-computed
observatory-ceres	observatory-ceres-computed
observatory-rings	observatory-arrokoth

Stars

Temperatures, color indices and light curves, which is most of what a star gives you from this distance -- plus a spectrum full of elements that should not be there, a jet at a quarter of light speed, a dip measured filter by filter, and two atmospheres cool enough that the visible band is almost the wrong place to look. The Planckian locus barely turns, so several of these are near-monochromes and say so. Four end states sit here too: a white dwarf's whole cooling track, the cold nothing at the end of it and the last supernovae in the universe, the blue-white star a red dwarf becomes after trillions of years, and the stars in a globular cluster that are hotter than their own age allows.

Scheme		from	ΔE	n	hue
observatory-albireo	the color-contrast doubles, and the green that isn't	measured	18.8	7	167
observatory-alphacentauri	the nearest three stars, and one flare	measured	16.9	5	168
observatory-betelgeuse	a resolved supergiant, mid-dimming, in amber	image	9.8	7	37
observatory-betelgeuse-computed	a supergiant, and the dust that dimmed it	measured	17.8	6	2
observatory-nervia	the star Eburonia orbits, which is very nearly the Sun	image	17.0	5	2
observatory-nervia-computed	the star Eburonia orbits, by its own temperatures	measured	12.3	8	97
observatory-carbon	the reddest stars there are, in purity not hue	measured	16.5	6	6
observatory-cepheid	a light curve, and no color to speak of	measured	15.4	5	3
observatory-etacarinae	two lobes of debris from a star that survived its own explosion	image	16.1	6	104
observatory-etacarinae-computed	the Homunculus, and the star inside it	measured	20.7	7	185
observatory-magnitude	the eight brightest stars, with Vega at zero	measured	15.8	8	171
observatory-sirius	brighter is cooler, for once	measured	11.2	6	3
observatory-v838monocerotis	a light echo, which is not an explosion but its shadow on dust	image	16.9	8	180
observatory-v838monocerotis-computed	one flash, seen at four delays	measured	16.3	7	192
observatory-boyajian	a dip in a light curve, measured filter by filter	measured	18.7	5	230
observatory-przybylski	a spectrum full of elements that should not be there	measured	28.3	9	282
observatory-ss433	one line, two jets, and the half that is invisible	measured	21.3	7	202
observatory-browndwarf	not a star, not a planet: a red monochrome	image	15.8	7	101
observatory-browndwarf-computed	the failed stars, and the one honest purple here	measured	17.5	6	145
observatory-wolfrayet	a star shedding itself, in plum and steel	image	16.2	6	144
observatory-wolfrayet-computed	the hottest stars there are, and none of it is the continuum	measured	15.7	7	225
observatory-crux	the Southern Cross, which is three quarters one color	measured	20.5	5	174
observatory-arcturus	the reference K giant, and the gaps in its light	measured	17.5	8	216
observatory-vega	the star everything else is measured against	measured	17.1	6	220
observatory-rigel	a blue supergiant, and the dust it lights	measured	16.7	7	198
observatory-deneb	one line, in emission and in absorption	measured	13.9	7	250
observatory-mira	the first variable, and the band that exaggerates it	measured	22.6	7	178
observatory-bluedwarf	a red dwarf's whole future, in six steps	measured	19.0	7	184
observatory-cooling	a white dwarf, from 100,000 K down to nothing	measured	17.8	7	171
observatory-blackdwarf	the coldest thing there will ever be, and its last light	measured	21.5	6	169
observatory-straggler	one cluster's diagram, and the stars that break it	measured	17.8	7	176

Gallery

observatory-albireo	observatory-alphacentauri
observatory-betelgeuse	observatory-betelgeuse-computed
observatory-nervia	observatory-nervia-computed
observatory-carbon	observatory-cepheid
observatory-etacarinae	observatory-etacarinae-computed
observatory-magnitude	observatory-sirius
observatory-v838monocerotis	observatory-v838monocerotis-computed
observatory-boyajian	observatory-przybylski
observatory-ss433	observatory-browndwarf
observatory-browndwarf-computed	observatory-wolfrayet
observatory-wolfrayet-computed	observatory-crux
observatory-arcturus	observatory-vega
observatory-rigel	observatory-deneb
observatory-mira	observatory-bluedwarf
observatory-cooling	observatory-blackdwarf
observatory-straggler

Exoplanets

Nobody has resolved any of these worlds, so each palette comes from the artist's impression the mission published, which is what a search returns. Six of them share artwork: NASA serves one illustration per planet class, so three super-Earths and two gas giants are drawn by the same files. Those schemes are shipped anyway, declared siblings, and each header says which frame it shares and with whom. Four of them are the planets people know by a name instead of a designation, and each of those has release art of its own.

Scheme		from	ΔE	n	hue
observatory-trappist	bone-dry rock in the habitable zone of a red dwarf	image	17.6	5	174
observatory-trappist-computed	seven worlds, and the one small red star lighting them	measured	16.4	7	2
observatory-tres2	the darkest world known, and the dimmest palette here	image	22.0	5	17
observatory-hd189733	the one exoplanet whose color was measured, and it is blue	image	15.6	7	23
observatory-eburonia	a hot Neptune in violet and indigo, and its orange dwarf	image	15.7	7	159
observatory-kepler56c	a red giant, and the planet it is about to swallow	image	9.2	8	69
observatory-kepler292b	a super-Earth as an ocean world, in teal and sea green	image	17.6	5	30
observatory-kepler20b	five planets ranged against Mercury's orbit	image	17.2	8	215
observatory-hd40307f	gray super-Earths under an orange dwarf	image	17.3	6	174
observatory-kepler90h	the eight-planet system, in olive and gold	image	9.4	7	25
observatory-mintome	the pink planet: a giant still glowing from its own formation	image	16.6	5	78
observatory-hd157172b	a hot Jupiter being eaten, and the star doing it	image	16.7	6	20
observatory-gliese3323b	sage and slate, with one steel-blue sea	image	16.7	6	205
observatory-kepler1275b	a frozen super-Earth in russet, at the edge of the light	image	9.8	4	31
observatory-kepler1328b	a terrestrial placeholder in tan and umber	image	17.6	4	25
observatory-kepler438b	a superflare sterilising a habitable-zone planet	image	16.5	5	26
observatory-kepler367b	an atmosphere streaming off a small planet, in indigo and amber	image	9.5	7	132
observatory-sweeps10	a Jupiter skimming a spotted red star, ten hours per year	image	16.8	6	42
observatory-enaiposha	a steam world in silhouette against a red dwarf	image	9.6	4	150
observatory-dimidium	the first planet found around a sun-like star, in tan and butterscotch	image	9.8	4	45
observatory-tatooine	two suns, one silhouette, and every color warm	image	9.4	5	29
observatory-osiris	a planet boiling away, gold against an ice-blue tail	image	16.8	8	181
observatory-methuselah	the oldest planet known, in teal and cobalt	image	17.4	6	190

Gallery

observatory-trappist	observatory-trappist-computed
observatory-tres2	observatory-hd189733
observatory-eburonia	observatory-kepler56c
observatory-kepler292b	observatory-kepler20b
observatory-hd40307f	observatory-kepler90h
observatory-mintome	observatory-hd157172b
observatory-gliese3323b	observatory-kepler1275b
observatory-kepler1328b	observatory-kepler438b
observatory-kepler367b	observatory-sweeps10
observatory-enaiposha	observatory-dimidium
observatory-tatooine	observatory-osiris
observatory-methuselah

Nebulae

Clouds of gas, sampled from the press image each one is known by and paired with the emission lines that image was taken through. Narrowband false color is the rule rather than the exception here: the filters that resolve a nebula's structure sit at wavelengths the eye does not separate, so the Hubble-palette version is both the only one and the familiar one.

Scheme		from	ΔE	n	hue
observatory-catseye	concentric shells in lilac and slate, eleven of them	image	17.4	5	136
observatory-catseye-computed	a planetary nebula's shells, ordered by ionisation energy	measured	23.4	9	288
observatory-crab	a supernova's wreckage: teal synchrotron under gold filaments	image	9.5	8	174
observatory-crab-computed	synchrotron continuum against line filaments	measured	12.5	8	216
observatory-helix	the Eye of God: a rust iris around a periwinkle pupil	image	9.2	8	187
observatory-helix-computed	the Eye of God, and the ten thousand knots in it	measured	26.1	7	221
observatory-trifid	three dust lanes across pink hydrogen, and a blue reflection	image	15.2	6	138
observatory-trifid-computed	one star, and the three things dust does to its light	measured	17.2	7	240
observatory-boomerang	the coldest known place, and it photographs as warm gray	image	18.2	8	102
observatory-boomerang-computed	one kelvin, which has no color, so this is borrowed light	measured	15.3	6	158
observatory-orion	the sharpest view of the nebula, in brick and rose	image	16.2	6	43
observatory-orion-computed	one constellation, measured	measured	16.7	7	234

Gallery

observatory-catseye	observatory-catseye-computed
observatory-crab	observatory-crab-computed
observatory-helix	observatory-helix-computed
observatory-trifid	observatory-trifid-computed
observatory-boomerang	observatory-boomerang-computed
observatory-orion	observatory-orion-computed

Galaxies and deep fields

Whole stellar populations, which average out paler than any single star; one cloud of gas that is genuinely green; the galaxy that was hardest to measure because we are inside it, both as an illustration and as a photograph from the ground; and two deep fields, Hubble's and Webb's.

Scheme		from	ΔE	n	hue
observatory-bimodal	galaxies come in two colors, and the gap is not green	image	18.8	7	152
observatory-hoag	a gold core inside a detached ring, and nothing in between	image	9.4	7	217
observatory-hoag-computed	an old core, a young ring, and nothing in between	measured	15.6	7	166
observatory-voorwerp	a green ghost lit by a quasar that has already gone out	image	17.7	5	145
observatory-voorwerp-computed	the one green thing, and it is gas rather than a star	measured	27.3	7	262
observatory-galaxy	color as age, across a spiral galaxy	image	17.0	7	171
observatory-milkyway	our own galaxy from outside, which nobody has seen	image	16.4	4	183
observatory-milkyway-computed	our own galaxy, whose color was the hardest to measure	measured	15.9	7	151
observatory-milkywayparanal	the galactic plane over Paranal, in slate and mauve	image	12.6	4	60
observatory-deepfield	ten thousand galaxies, and four per cent of the frame is lit	image	9.4	7	223
observatory-deepfield-computed	ten thousand galaxies, sorted by how long the light took	measured	27.3	6	210
observatory-deepfieldwebb	the first Webb deep field, in amber and steel	image	15.8	6	167

Gallery

observatory-bimodal	observatory-hoag
observatory-hoag-computed	observatory-voorwerp
observatory-voorwerp-computed	observatory-galaxy
observatory-milkyway	observatory-milkyway-computed
observatory-milkywayparanal	observatory-deepfield
observatory-deepfield-computed	observatory-deepfieldwebb

Events

Things that happened, or are still happening. Two of these are the same black hole four years apart, two are the same afterglow of the Big Bang five years apart, and one is a grayscale: the black-hole image with its color map taken off, which is the closest thing to what was recorded. The explosions are the other half: three supernovae sampled from the X-ray and infrared frames their observatories lead with, the dust echoes of the brightest gamma-ray burst on record, and a nova, which is the one transient here that is over too quickly to have a portrait and is derived from its light curve instead.

Scheme		from	ΔE	n	hue
observatory-eventhorizon	the first photograph of a black hole, and it is all one hue	image	16.3	7	40
observatory-eventhorizon-computed	the colormap the black hole pictures used	measured	16.9	8	58
observatory-jet	the same hole four years later, in violet, with its jet	image	9.3	8	132
observatory-shadow	the black hole picture as recorded, which is gray	image	11.3	3	0
observatory-cosmicbackground	the oldest light there is, as a temperature map	image	17.7	8	178
observatory-cosmicbackground-computed	a diverging scale, cold to hot, like the anisotropy maps	measured	11.0	8	201
observatory-cosmicbackgroundlegacy	the last word on the oldest light, in eight colors	image	17.3	8	170
observatory-kilonova	two neutron stars merging, and where the gold came from	image	17.1	7	185
observatory-kilonova-computed	a photosphere crossing the whole stellar locus in five days	measured	13.6	6	171
observatory-supernova1987a	the nearest supernova in four centuries, ringed	image	17.8	5	195
observatory-cassiopeia	a remnant in X-rays, which makes it violet	image	17.9	8	234
observatory-cassiopeiawebb	the same remnant in the infrared, which makes it teal and rust	image	9.5	8	207
observatory-tycho	the star that proved the heavens change, in crimson and periwinkle	image	16.9	8	96
observatory-nova	a white dwarf's surface igniting, hour by week	measured	17.8	8	233
observatory-brightestofalltime	the brightest burst ever recorded, in dust echoes	image	9.7	6	40

Gallery

observatory-eventhorizon	observatory-eventhorizon-computed
observatory-jet	observatory-shadow
observatory-cosmicbackground	observatory-cosmicbackground-computed
observatory-cosmicbackgroundlegacy	observatory-kilonova
observatory-kilonova-computed	observatory-supernova1987a
observatory-cassiopeia	observatory-cassiopeiawebb
observatory-tycho	observatory-nova
observatory-brightestofalltime

Readings

What an instrument recorded rather than what a body looks like, so there is no portrait to be faithful to: a spectrum, a diagram, a population, a photographic emulsion. Hue, and in several cases brightness too, comes from the measured quantity itself, and where the derivation fixes the order of the ladder the solver may respace it but never reorder it.

Scheme		from	ΔE	n	hue
observatory-balmer	the hydrogen Balmer series, brightness following line strength	measured	10.8	7	176
observatory-doppler	one spectral line, seven velocities	measured	10.6	8	265
observatory-pulsar	maximum contrast, and pale because of it	measured	10.3	7	224
observatory-fraunhofer	the Sun's own labelled absorption lines	measured	29.7	10	286
observatory-meteor	what the rock was made of, while it lasted	measured	30.4	8	207
observatory-hertzsprungrussell	a color-magnitude diagram, both axes used	measured	17.5	7	172
observatory-extinction	one blue star behind seven columns of dust	measured	15.5	7	171
observatory-kuiper	two populations, and the gap between them	measured	16.8	8	15
observatory-plate	no color at all, and the five grays that leaves	measured	12.2	4	0

Gallery

observatory-balmer	observatory-doppler
observatory-pulsar	observatory-fraunhofer
observatory-meteor	observatory-hertzsprungrussell
observatory-extinction	observatory-kuiper
observatory-plate

Constructions

Of nothing at all, and built to a specification instead: the contrast ladder is fixed and the hues are computed, subject to a separation floor and a minimum distance in the chroma plane.

Scheme		from	ΔE	n	hue
observatory-albedo	the solar system, lit by apparent magnitude	solved	10.8	8	201
observatory-dichroic	legible with red-green and blue-yellow color blindness	solved	14.2	7	248
observatory-horizon	one line falling into a black hole	solved	10.5	9	267
observatory-lagrange	the palette solved for maximum separation	solved	19.1	10	270
observatory-phi	hues at the golden angle, so any subset stays spread	solved	20.4	10	296
observatory-syzygy	separation spent where tokens actually touch	solved	15.5	10	304

Gallery

observatory-albedo	observatory-dichroic
observatory-horizon	observatory-lagrange
observatory-phi	observatory-syzygy

📓 Recipes

A random scheme, or one filtered by subject and by how far apart its colors are:

local pool = vim.tbl_filter(function(s)
  return s.family == "star" and s.floor >= 16
end, require "observatory.schemes")
vim.cmd.colorscheme(pool[math.random(#pool)].name)

Stepping through the collection from a keymap, each one announcing itself:

local function step(delta)
  local schemes = require "observatory.schemes"
  local at = 0
  for i, s in ipairs(schemes) do
    if s.name == vim.g.colors_name then
      at = i
      break
    end
  end
  local s = schemes[(at - 1 + delta) % #schemes + 1]
  vim.cmd.colorscheme(s.name)
  vim.notify(("%s -- %s"):format(s.name, s.about))
end

vim.keymap.set("n", "]o", function()
  step(1)
end)
vim.keymap.set("n", "[o", function()
  step(-1)
end)

A picker with nothing installed, over vim.ui.select:

vim.api.nvim_create_user_command("Observatory", function()
  vim.ui.select(require "observatory.schemes", {
    prompt = "colorscheme",
    format_item = function(s)
      return ("%-32s %s"):format(s.name, s.about)
    end,
  }, function(s)
    if s then
      vim.cmd.colorscheme(s.name)
    end
  end)
end, {})

Comparing a photographed subject with the calculation of the same subject:

local schemes = require "observatory.schemes"
local known = {}
for _, s in ipairs(schemes) do
  known[s.name] = true
end
for _, s in ipairs(schemes) do
  if s.method == "sampled" and known[s.name .. "-computed"] then
    print(s.name, s.about)
  end
end

Dedicated picker with mini.pick:

MiniPick.registry.observatory = function()
  local obs = require "observatory"
  local items = vim.tbl_map(function(s)
    return { text = ("%-22s %-12s ΔE %4.1f  %s"):format(s.name, s.family, s.floor, s.about), name = s.name }
  end, require "observatory.schemes")
  local restore = vim.g.colors_name
  return MiniPick.start {
    source = {
      items = items,
      name = "observatory",
      choose = function(item)
        vim.cmd.colorscheme(item.name)
      end,
      preview = function(_, item)
        obs.load(item.name)
      end,
    },
  } or (restore and vim.cmd.colorscheme(restore))
end

📜 License

See LICENSE.