Knowledge base
Install & set up
Getting Nocturne onto your machine, and pointing it at the tools it drives. Nothing here is required to start — Nocturne opens an image and runs the whole pipeline with none of it — but two free downloads make a real difference to the result.
Install Nocturne
Every release, for both platforms, is on the downloads page. Nocturne is free and open source under the GPL; there is no account and no licence key.
macOS
Apple Silicon (M1 or newer) — there is no Intel build. Download the zip, unpack it and drag Nocturne to Applications.
It isn't notarized, so on first launch macOS will refuse to open it. Right-click the app → Open → Open, or allow it once under System Settings → Privacy & Security. You do this once, ever.
Linux
x86-64, shipped as a tarball. There is nothing to install — unpack it anywhere and run the binary inside:
tar -xzf Nocturne-<version>-linux-x86_64.tar.gz
./Nocturne/NocturneThe build host is Ubuntu 24.04, so it needs glibc 2.39 or newer.
That covers Ubuntu 24.04 and later, Debian 13, Fedora 40+ and current rolling distributions;
it will not start on Ubuntu 22.04. Check yours with ldd --version.
Tested on Xubuntu 24.04. Other desktops should be fine — it is a Qt application and asks nothing unusual of the system.
What happens on first launch
Nocturne scans the usual install locations for the tools below and fills in any it finds, so on a typical machine there is nothing to configure. It also asks once whether it may send an anonymous usage count — there is no identifier of any kind behind it, and declining changes nothing about how the app works. See privacy for exactly what that is and isn't.
The external tools
Nocturne drives a few best-in-class tools rather than reinventing them. They install separately — Nocturne never bundles them, because their licences do not allow it — and you point it at each one in Settings.
If you install two things, make them GraXpert and StarNet2. Both are free, and between them they cover gradient removal and star separation — the two jobs where the built-in fallbacks are noticeably weaker than the real thing.
GraXpert free
Free and open source (GPL-3.0). Powers background & gradient extraction — removing light-pollution glow and vignetting — and is one of the available denoise engines.
- Download from graxpert.com.
- macOS — the .app, Apple Silicon or Intel. Drag it to Applications and Nocturne finds it on its own.
- Linux — a zip containing a folder with a
GraXpertexecutable at the top; there is no installer, so wherever you unpack it is the install. Unpack it to~/Applications/GraXpert-linux/and Nocturne finds it; an AppImage in~/Applications/works too.
StarNet2 free
Separates an image into a starless frame and a stars layer. That one job is behind more of Nocturne than anything else on this page — Star Reduction, De-green Stars, Nebula Saturation, Narrowband, Starless Levels, Star Colour, Sharpen Nebulosity, Upscale Crop, Auto Enhance, Colour Balance and the starless+stars export all need it.
Without it those steps fall back to Nocturne's own separator, which works but leaves roughly twice as much star flux behind — in practice, grey blobs where the bright stars were. StarNet2 costs nothing, so there is little reason to accept that.
- Download from the StarNet CLI tools page. Take the CLI package — the PixInsight module on the same site is a different thing and Nocturne cannot drive it.
- macOS — the
.pkginstaller is easiest and puts it in/usr/local/bin. The portable zip works too; unpack it under~/Applications/and keep the executable and its weights folder together. - Linux — the
.deb(sudo apt install ./StarNet2_linux_*.deb), or the CLI zip unpacked to~/Applications/.
Not bundled, and it never will be: StarNet2's licence is non-transferable and grants no redistribution. Free to download, free to use.
ASTAP free optional
A free plate solver. It works out exactly where a frame points, which unlocks target identification, annotation (object labels, compass, scale bar), photometric colour calibration and mosaic stacking.
- Download from the ASTAP page —
a macOS build and a Linux
.deb. - You also need a star database. On the same page, download D05 and install it as directed — that's the right one for a smart telescope's field of view. ASTAP without a database solves nothing.
- In Nocturne, open Settings → ASTAP and press Test to confirm it's found.
RC-Astro optional · paid
Russell Croman's BlurXTerminator (deconvolution/sharpening), NoiseXTerminator (denoise) and StarXTerminator (star removal) are the gold standard, and Nocturne uses them if you have them. Every step that can use RC-Astro also works without it — StarXTerminator's job falls to StarNet2, and the rest to Nocturne's own code.
- Purchase and download from rc-astro.com (one-time purchase; macOS and Linux builds; see the site for current pricing).
- Nocturne drives the standalone versions — you don't need PixInsight or Photoshop. Set the path in Settings, and choose your denoise engine there too.
Pointing Nocturne at them
Open Settings. Each tool has a row with its path, a Browse… button, a Test button that actually runs the tool, and a Download ↗ link if you haven't got it yet.
Rescan for installed apps re-checks the standard locations. It only fills in rows that are empty or broken — a path you set by hand is never overwritten, on the principle that if you found the thing yourself you had a reason.
These are the places Nocturne looks on its own:
| Tool | macOS | Linux |
|---|---|---|
| GraXpert | /Applications/GraXpert.app |
~/Applications/GraXpert-linux/GraXpert, /opt/GraXpert*, an AppImage, or PATH |
| StarNet2 | /usr/local/bin/starnet2, ~/Applications/starnet2*/ |
/usr/bin/starnet2, ~/Applications/starnet2*/, or PATH |
| ASTAP | /Applications/ASTAP.app, /opt/homebrew/bin/astap |
/usr/bin/astap, /opt/astap/astap, or PATH |
| RC-Astro | /Applications/RC-Astro/CLI/rc-astro |
/opt/RC-Astro/CLI/rc-astro, ~/Applications/RC-Astro/CLI/rc-astro |
Anywhere else is fine — that's what Browse… is for. The list is only what gets found without being told.
If something isn't found
“Set, but cannot be run.” The path points at something that isn't
executable. On Linux that is usually a missing execute bit after unpacking:
chmod +x the binary. On macOS it can be quarantine — open the tool once from
Finder and allow it.
Installed, but Rescan doesn't see it. Point at it with Browse… and it will stay. If the tool lives somewhere common that we miss, say so and it gets added to the list.
A step seems to do nothing. Star-based steps without StarNet2 or RC-Astro fall back to the built-in separator, and on a star-poor frame the difference can be hard to see. Settings will tell you which engine is actually in use, and the provenance report records it for every step you ran.
GraXpert or StarNet2 runs but takes a long time. Both are doing real neural-network work on a full-resolution frame. Ten to sixty seconds is normal; Nocturne shows progress and stays cancellable throughout.
Still stuck? The FAQ covers the common ones, and issues go on GitHub.
Set up? Read the guide — what each step in the pipeline actually does, and how to choose between the options it offers.