Status: still in active development. Contributions are very welcome — testing against real cameras/mounts, feature proposals, code, bug reports, anything. If you have ZWO (or other) camera or astro gear you'd be willing to lend or send to the author for compatibility testing, that's especially appreciated — please reach out via Issues. Open and resolved issues are also browsable right inside the app — Settings > Community.
Website · Features · Architecture · Design Notes · Distribution · Screenshots · Examples · Changelog · Contributing · License · Releases · Issues
Repository: github.com/giulioroggero/skyformac
Skyformac is a native macOS astrophotography capture app for ZWO ASI cameras — built directly on the ZWO ASI Camera SDK, no ASCOM/INDI bridging layer. Think of it as a SharpCap-style capture tool for the Mac: connect a camera, get a live preview, adjust gain/exposure/binning and the rest of its controls, and capture single exposures, dark/flat calibration frames, live stacks, or lucky-imaging bursts, straight to FITS/PNG/TIFF.
If you don't have a ZWO camera to hand, an iPhone (via Continuity Camera) or any other USB webcam works as a live source too — handy for afocal eyepiece projection on the Moon and bright planets.
Most software that can drive a ZWO ASI camera — SharpCap, FireCapture, and others — is Windows-native or Java-based, running on a Mac only through Wine/Parallels or a JVM, neither of which was built with this hardware or this OS in mind. Skyformac is a ground-up SwiftUI/AppKit app instead, which is what makes a few things possible that a ported or cross-platform tool generally can't do as directly:
- Real GPU acceleration, not a CPU fallback. Debayering, the display
stretch, denoise, wavelet sharpening, histogram computation, and
live-stacking all run as actual Metal compute shaders (
Shaders.metal) on Apple Silicon's GPU — a cross-platform tool's fast path is typically DirectX-only, leaving macOS on a slower CPU-only code path even when it runs at all. - An iPhone as a capture source, natively. Continuity Camera — using a paired iPhone as a live afocal-projection camera, with real focus-lock and frame-stacked Night Mode support — is an Apple-ecosystem capability tied to macOS/iOS; it isn't something a cross-platform or Windows-native tool can offer at all, on any OS.
- Apple's Vision framework for real detection, not a bundled third-party computer-vision library — star/streak/planet detection and the live WCS solve all go through the same system framework macOS itself uses for on-device vision tasks.
- Swift's actor model enforces the hardware-threading rules other apps
only document. Every blocking ZWO SDK call is structurally isolated onto
CaptureEngine's own actor — not just a convention to remember, but something the compiler checks — which is what keeps a multi-second USB handshake or a long exposure from ever freezing the UI (seedocs/design-notes.mdfor the real hangs this caught and fixed during development). - Runs entirely locally. No telemetry, no cloud account, no network dependency for anything the camera itself doesn't need — and the source is open (GPLv3, see License below), so any of this is independently verifiable rather than taken on faith.
- macOS 14.0+ to run the app.
- To build it yourself: Xcode 26+ (Swift 6), and the Metal toolchain component
(
xcodebuild -downloadComponent MetalToolchain— needed once, to compileShaders.metal). - A ZWO ASI camera connected over USB, or a webcam/iPhone — see Connecting a camera below for what to do without either.
The GitHub releases and
the website both ship a
skyformac-vX.Y.Z-macOS.dmg (recommended — a standard drag-to-Applications
installer) and a skyformac-vX.Y.Z-macOS.zip with the same contents, for
anyone who prefers a plain zip. Skyformac isn't notarized by Apple yet (that
needs a paid Apple Developer Program membership — see
docs/distribution.md), so the first time you open it
macOS Gatekeeper will refuse to launch it and say it "cannot be opened because
the developer cannot be verified" (or, once a browser has quarantined the
download, "is damaged and can't be opened").
Both the .dmg and the .zip include a Fix Gatekeeper Warning.command
file alongside skyformac.app to clear this automatically:
- Open the
.dmgand dragskyformac.apponto theApplicationsshortcut inside it, like any normal Mac app install. - Double-click
Fix Gatekeeper Warning.command(still inside the mounted.dmgwindow) — it opens a Terminal window and closes on its own once done. - Open
skyformac.appfrom/Applications— it now opens normally.
- Unzip the download.
- Double-click
Fix Gatekeeper Warning.command(it opens a Terminal window and closes on its own once done). It:- Moves
skyformac.appinto/Applicationsif it isn't there already. Running it straight out of~/Downloadswhile quarantined triggers macOS's App Translocation, which silently breaks Camera permission prompts for the iPhone/webcam source (the ZWO ASI camera isn't affected, since it doesn't need that permission at all). - Clears the quarantine flag.
- Resets the Camera permission, since ad-hoc signing makes the app's signature change on every release, which can otherwise leave macOS stuck denying access with no re-prompt. You'll just be asked to allow Camera access again the first time you connect a webcam.
- Moves
- Open
skyformac.appfrom/Applications(Launchpad, Spotlight, or double-click it there) — it now opens normally.
If macOS still won't run the script itself, right-click it, choose Open, then confirm Open in the dialog — the same one-time trust step as any unsigned app. You can also do the fix by hand from Terminal:
xattr -dr com.apple.quarantine skyformac.app
make build # build into ./build
make test # run the unit tests (skyformacTests) and UI tests (skyformacUITests)
make run # build and launch skyformac.app
make clean # remove ./build
make open # open the project in Xcode
make alone runs build; see make help for the full list. Or open
skyformac.xcodeproj in Xcode and run/test normally (⌘R / ⌘U) — the Makefile
just wraps the equivalent xcodebuild invocations with a pinned
-derivedDataPath ./build.
CI (.github/workflows/ci.yml) runs make build/make test on GitHub Actions'
macos-15 runners on every push/PR.
The sidebar's Cameras list shows any ZWO ASI camera currently connected over USB — click Connect. Below it, iPhone / Webcam lists Continuity Camera and other AVFoundation sources (an iPhone needs to be wired over USB, or nearby and signed into the same Apple ID for wireless Continuity Camera); click Connect there for a webcam/iPhone source instead. Use the refresh button at the top of the sidebar to rescan either list.
Once connected, the toolbar's status pill shows the connection state and ZWO SDK version, and the main pane starts streaming a live preview. Wizard/Load Preset buttons sit right next to Disconnect on a connected ZWO camera's own row, and a fuller Acquisition section (Wizard/Save Preset/Load Preset/Reset to Default) appears right below the camera list — so a target setup, a saved preset, or undoing everything back to defaults is one click away without hunting through the Controls panel's tabs. Right above that, a Running status list shows every currently-active pipeline (Live Stack, Lucky Imaging, Recording to Disk, SER recording, Planetary Tracking, Polar Alignment, Cloud Sentinel, Focus Assist) — whether or not its own tab happens to be showing on the right — each with a one-click jump to its controls and a one-click Stop.
- GPU / CPU toggle (⌘M) — switches between the Metal (GPU compute shader) and CGImage (CPU) render paths for debayer/stretch/histogram. GPU is the default; denoise, wavelet sharpening, and GPU live stacking need it on.
- Night Mode (⌘⇧N) — a red-only tint on the surrounding UI (sidebar, Controls panel, Histogram/Curves, the preview's own overlay chrome) to preserve dark adaptation, deliberately leaving the live image itself untinted — the whole point of the app is seeing the real sensor data.
- All-Sky Monitor (⌘⇧A) — a picture-in-picture feed from a secondary webcam or nearby iPhone, independent of the main capture pipeline, for keeping an eye on clouds or cabling. Has its own brightness/motion alerts.
- Pinch (or the zoom badge) to zoom into the preview 1×–8×, drag to pan once zoomed in; double-click to reset.
- The format picker (RAW8/RAW16) appears when the connected camera supports more than one; webcam/iPhone sources are always RGB24, so it's hidden then.
- Below the preview, a Histogram/Curves tab pair: the histogram has a "By Channel" toggle (any color source) that swaps the combined black/white view for separate Red/Green/Blue curves and switches the Black/White Point sliders to three fully independent pairs, for correcting a color imbalance (e.g. a light-polluted sky's orange cast) right at the stretch stage. Curves is Photoshop-style tone-curve grading — a master RGB curve plus independent Red/Green/Blue curves layered on top of it, applied as a post-stretch pass on both render paths, off by default. A "Detach" button pops both into a separate floating panel that can overlap the main window and stay open.
The right-hand panel is split into four tabs (a vertical icon strip on its trailing edge — also reachable from the menu bar's Sidebar Tab menu, ⌘1-⌘4). Camera Controls/Improvements are grouped by what each control affects (raw hardware vs. display-only effects); Planetary/Deep Sky are grouped by imaging genre instead, since mixing both genres' workflow tools in one long list made it hard to navigate — Focus Assist appears in both, since it genuinely serves either:
Camera Controls — raw hardware, nothing here is a display effect:
- Dynamic per-camera controls (gain, offset, cooler, flip, binning, etc. — whatever the connected ZWO camera actually reports), plus one-tap Gain/Offset Presets (ZWO's own Highest Dynamic Range/Unity Gain/Lowest Read Noise recommendations) and a live dropped-frame counter.
- Single Exposure — a log-scale slider spanning microseconds to tens of seconds (real ASI exposure ranges don't fit a linear slider), with a live countdown next to Capture (and Calibration's Capture Dark/Capture Flat, timed the same way) so a long exposure's remaining time is never a guess.
- iPhone / Webcam (webcam sources only) — Lock Focus (freezes the device's own autofocus, which otherwise fights afocal projection) and Night Mode (10s/60s frame-stacked simulated long exposure).
- Export — PNG/TIFF/FITS, for the current frame or a stack. FITS exports
from a color camera embed a
BAYERPATheader card (the same convention PixInsight/Siril/SharpCap use), so a re-opened file knows how to debayer. - Exported Files — a persistent (survives a relaunch) history of every export/recording this app has written, plus an Open File… button (or just drag a file onto the window) for any FITS/PNG/TIFF/JPEG file. Opening a FITS file re-renders it through the app's own debayer/stretch pipeline with adjustable Black/White Point sliders — a viewer, not an editor; real elaboration (stacking, plate solving, wavelet sharpening at full strength) still belongs to a dedicated tool. Exporting while Live Stack is running exports the actual stacked average, on both render paths.
Improvements — opt-in visual effects, never baked into exported/recorded raw data:
- Image Enhancement — real-time denoise (bilateral filter) and wavelet sharpening, as Metal compute kernels (CPU fallback when GPU rendering is off) — works for both ZWO mono and iPhone/webcam color sources.
- Live GPU Enhancement Controls — a separate three-stage pipeline (GPU only): temporal + spatial denoise, then a non-linear contrast stretch.
- AI & Machine Learning Suite — satellite/aircraft trail masking and a Cloud Cover & Drift Sentinel.
- One "Disable All Improvements" checkbox falls back to the camera's own unmodified output in a single click.
Planetary — the small-ROI, high-FPS, burst/video capture workflow:
- Focus Assist — live star detection with a sharpness/HFD readout; turn on Recognize Stars underneath it to identify which catalog stars are in frame and (once identification is confident enough) show real catalog-object badges over the live view. (Also in Deep Sky.)
- Planetary Auto-Center — Vision-tracked disk with an optional auto-cropped ROI.
- Planetary Presets (ZWO only) — one tap sets RAW8, a small Capture ROI, and a safe starting exposure/gain for Saturn/Jupiter/Mars/Venus/the Moon, tuned around a modern ~2µm-pixel planetary camera (e.g. ASI678MC) behind a reference Maksutov 127mm/1500mm (f/11.8). A Telescope picker (a curated list of common Maksutovs/SCTs/Newtonians/refractors) scales the starting exposure for a different telescope's focal ratio — camera sensitivity isn't accounted for, so these stay starting points to fine-tune against the live histogram either way.
- Acquisition Wizard (⌘⇧W) — pick a target (Moon, Venus, Mars, Jupiter, Saturn, or a curated deep-sky list: M13/M56/M31/M42/M45/M51/M57/M27/M81/M8) and set up ROI, gain, exposure, and Live Stack/Reduce Drift/Smart Live Stack/Mesh Drift Correction (Experimental)/Lucky Imaging for it in one step — the Moon uniquely turns on both Live Stack and Lucky Imaging at once. Works for an iPhone/webcam source too (Live Stack/Lucky Imaging/Smart Live Stack apply; ROI/gain/exposure/ Reduce Drift don't, and the Wizard says so). Save Preset…/ Load Preset… (⌘⇧S/⌘⇧L, Camera menu, or the Cameras sidebar's own "Acquisition" section) round-trip a setup to its own JSON file, one file per preset — and work standalone, without the Wizard sheet open at all: Save snapshots whatever's currently configured, Load applies a file immediately.
- Capture ROI (ZWO only) — a smaller-than-full-sensor region increases achievable frame rate directly (less data read off the sensor per frame), the classic "small ROI, high FPS" planetary/lunar technique. Quick presets or a custom width/height/center — genuinely centered on the sensor (or wherever you place it), not pinned to its top-left corner. The live preview's own refresh rate is capped independently (~30fps) so a very small, very-high-frame-rate ROI can't flood the display into a growing, flickering backlog — recording and Lucky Imaging still see every real frame regardless.
- Record SER Video (ZWO only) — writes every incoming frame, undiscarded,
into a single
.servideo for a set duration — the raw-video container AutoStakkert!3/PIPP/RegiStax expect to do their own alignment and best-frame selection from. - Lucky Imaging — burst capture, keeping only the sharpest fraction, stacked. Pause/Resume and Cancel Burst work mid-capture; Save Stacked Image… saves the result directly; Browse Frames… lists every captured frame by sharpness rank and previews/saves one specific frame instead of only the averaged stack.
- One "Disable All Planetary Features" checkbox falls back to the camera's own unmodified output in a single click.
Deep Sky — the long-exposure, many-subs workflow:
- Focus Assist — same as Planetary's; genuinely useful before either kind of session.
- Smart Exposure — measures read noise and sky background from real frames and recommends a sub-exposure length.
- Polar Alignment — two-frame rotation-center solve from star correspondences, with a live on-screen correction vector.
- ST4 Guiding — manual pulse-guide correction buttons (North/South/ East/West), shown only for cameras reporting a real ST4 port. Untested against real guiding hardware — no ST4-cabled mount has been available to confirm a pulse produces a real correction end to end.
- Calibration (Dark/Flat) — capture and manage any number of named dark and flat frames; toggle subtraction/correction independently (GPU or CPU, matching the active render path).
- Live Stack — running-average stacking of the live feed, with an optional GPU-only Reduce Drift (single-star lock-on alignment, background-subtracted centroid tracking, re-acquires on a lost lock) for mounts that don't track perfectly, e.g. alt-azimuth, or its "Experimental" alternative Mesh-Based Drift Correction — tracks an NxN grid of points instead of one locked star, triangulating the mesh and blending each triangle's drift with barycentric interpolation, so it can correct for field rotation and differential drift a single global shift can't. A live preview overlay shows the actual tracked grid and displacement vectors. A Pause/Resume to freeze and actually look at a running stack without discarding it, and a one-click Save Stacked Image… PNG snapshot. Smart Live Stack (Autopilot) turns it into a live, self-curating stack — automatically skips frames softer than the session's best or flagged by Cloud Sentinel, with a live kept/rejected count and a real estimated-SNR-gain readout for judging when it's no longer worth continuing.
- Record to Disk — continuous recording with a GPU sharpness gate (only writes frames sharp enough to be worth keeping) and a disk-space guardrail.
- One "Disable All Deep Sky Features" checkbox as above, plus stops any active recording.
In-app Help (⌘?) covers every one of these in detail, with full-text search and a "?" shortcut next to each setting that jumps straight to its explanation.
The Projects browser — an iMovie-style library of projects grouping sessions under a shared goal ("see M13, M57, Saturn") — is the app's main window whenever no session is running: there's no camera view to switch to without one. The Home page's toolbar switches between a grid of cover- thumbnail cards (default, one per project, generated from its most recent capture) and a sortable table (name, goal, session/capture counts, location, tags, last activity) — either way each project shows more than just its name. "New Project…" (Home page toolbar, or the menu bar's Project menu) is the only modal in the feature — it requires a name up front, so the project's name is always visible. Quick Start (Home page toolbar or the Project menu) skips that for a one-off outing: pick a planet, the Moon, or a curated deep-sky object and both a project and session are created automatically, with the target's recommended camera setup applied, straight into the camera view.
Clicking any session — run or not — opens its own full-width Session page (a
"Back to Project" button sits at the top, matching the equally full-width
Project Detail and Capture pages — no capped/centered Form margins
anywhere in the browser); the camera view only ever opens via an explicit
Run/Resume button, never just by tapping a row. Each session gets its own
folder for captures and settings, a timeline of thumbnails (oldest to most
recent, left to right, matching the Home page's own Observation Timeline;
each with its capture kind and, if present, a note underneath),
tags, notes, and GPS or hand-entered location, plus a full History
(date/time, position, aim, objects) and a capture-count Stats breakdown
shown in a real resizable/auto-sizing Table, not a cramped fixed grid.
Every capture also gets an automatic plain-English note — "Captured Saturn
in Live Stack as FITS," "Recorded M13 as an SER video for 30 sec" — built
from what was actually happening at the moment it was taken. Tapping a
timeline thumbnail opens its own Capture page — a larger preview, file info,
and the session's own context and stats. Exporting a frame or finishing a
SER recording while a session is running also files a copy into that
session's timeline. While running, a breadcrumb (Home / Project name /
Session name) replaces the window's usual
title-bar navigation, and the menu bar's Project menu covers every
project/session action — ending the session, opening the next one, adding a
new one, deleting it, switching projects — without a trip back to the
browser. "Ask AI to Plan…" sends a one-line goal to a local Ollama server and
shows the suggested session(s) before creating anything — it prefers
qwen3:8b when installed, otherwise whatever's actually installed, and
waits up to 3 minutes for a slower local model.
A project's own Danger Zone can Archive it (hidden from Home, restorable from the toolbar's Archived button) or Delete it — deletes move to Recently Deleted (toolbar) for a 30-day grace period before being purged automatically, with Restore and Delete Permanently (individually or all at once) available immediately.
Projects, sessions, and individual captures can be rated 1-5 stars, and
projects/sessions can be marked as favorites, which pin them to the top of
their list. The menu bar's File menu can Save As Project…/Load
Project… — packaging a project's whole folder (metadata, every session,
every capture file) into one .zip for handing to another user or machine,
always importing as a brand-new project so it can never collide with one
already in your library.
The Projects page's toolbar has a third view alongside the thumbnail grid and table: an Atlas — every session across every project plotted on a right-ascension/declination sky chart by its planned target's real position (matched against the app's own bundled Messier/Caldwell/bright-star catalog), filterable by project, object, or date range, with a tap to jump straight to that session.
Every capture's context menu (Session timeline, Capture Detail page) offers tools for turning a raw capture into a finished image, without leaving the app:
- Post-Process…, on any
.serrecording — a native planetary/lunar lucky-imaging pipeline: quality-scoring and registration against the sharpest frame, median/mean stacking of whichever fraction scored best, à trous multi-scale wavelet sharpening, RGB channel alignment, and auto-stretch. Runs as a background, cancellable job with live progress, GPU-accelerated where available, with an optional pass through GraXpert (star reduction/deconvolution/ background extraction) without leaving the modal. - Edit Image…, on any single FITS/PNG/TIFF capture — brightness, contrast, saturation, a gamma curve, crop, rotate, sharpen, denoise, and three astrophotography-specific tools: green color-cast removal (SCNR), star-size reduction, and shadow/highlight recovery. A one-tap Magic Wand auto-fix picks a starting point, every slider has its own reset, and a zoom/pan control checks the result at real pixel scale. Saves as a new Elaborated Image alongside the original.
- Live Capture — like an iPhone Live Photo: buffers a few seconds of the live feed, then scrub through every frame it captured and export whichever one actually looked sharpest, instead of timing one manual capture.
- Open in Siril…, on a session or a raw FITS/
.sercapture — hands it to a locally-installed copy of Siril's command-line tool for stacking/registration/stretching (single-frame debayer+stretch, planetary stack-without-registration, or deep-sky register+stack, auto-suggested from the target but always overridable), bringing the result back into the project's own Elaborated section. Off by default — enable it in Settings, since Siril itself is a separate app, not bundled.
See the Screenshots section below for Edit Image and Siril in action.
A chat panel on the right of every page (⌘⇧J to toggle) — the Dashboard, Projects, a Project/Session page, and the live camera view all share the same conversation, talking to a local Ollama server (nothing leaves your machine). It's grounded in whatever's currently relevant: the project/session you're viewing, the connected camera, and your own activity/ratings/favorites. Ask it a question, or ask it to create a project, create a session, or change the camera's gain/exposure/mode — any proposed change always shows its own Approve/Reject card first, nothing is applied automatically. It can also propose a whole next session (not just an object) as a "Suggested Session" card on the Dashboard, governed by an editable "skill" — standing instructions like "favor deep-sky over planetary" — tunable in Settings without touching a prompt in code. Minimize collapses it to a thin rail; Detach pops it into its own floating, resizable window; while the camera view is running it's always detached so it doesn't crowd the live preview, returning to the sidebar automatically once you're back to browsing if that's where it was.
The Home page toolbar's Equipment button (or the menu bar's own Equipment → View/Add New…) manages named equipment systems — "Backyard Rig," "Travel Setup" — each built from items across camera/mount/ optical tube (always shown, since every real setup has them) and optional categories (tracking system, imaging & optics, autoguiding, power & control, eyepiece, smartphone mount, other). Pick from a curated catalog of common brands/models or add a custom one by hand; a system can hold more than one item of the same category (a main scope plus a guide scope). A project can be assigned a system on its own Detail page; each session inherits that by default and can pick a different one for itself. Equipment systems are stored as their own files under a configurable Equipment folder (Settings), the same one-file-per-item approach the Projects folder already uses.
The Home page's Filters button narrows the project/session list (on top of free-text search) to an exact tag, an exact observed object (planets, the Moon, the bundled Messier/Caldwell/bright-star catalog, or anything already typed into a project), an equipment system, and/or a date range.
skyformac → Show Log… (⌘⇧D) — every connection event, error, Quick Start, and Ollama planning failure, timestamped, in one window. Select and copy any line, or use Copy All/Export… to grab the whole log when reporting a problem.
First connection to a USB ASI camera may prompt via System Settings → Privacy & Security — keep the camera connected when you grant it. Using a webcam/iPhone source, or the optional All-Sky Monitor, requests separate camera access the first time each is used; declining either leaves the rest of the app unaffected.
A quick visual tour of the app itself, following the same path as Using Skyformac above — the Dashboard and its Observation Timeline, Quick Start, a project's own page (with its zoomable Activity Timeline), a session's page and capture timeline, a single capture's detail page (Camera Settings, Prev/Next), Edit Image, sending a capture to Siril, Insights, and an Equipment system.
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The full, kept-up-to-date catalog of every picture/video is
EXAMPLES.md — below is just the original first-light session.
First real first-light test session — August 10, 2026, from a not-so-dark suburban sky, on a Maksutov 125/1500mm on an alt-azimuth mount, with a ZWO ASI 678MC. No dark/flat calibration, no stacking beyond the app's own live GPU enhancement pipeline — straight off the live view.
Arcturus — an initial bright-star test to confirm focus and framing before hunting anything fainter. High gain (402) and a not-so-dark sky show up as real sensor/sky noise here, which is expected and exactly what this shot was for:
▶ Watch the live-view recording (94s, 3018×1902)
M13 (Hercules Globular Cluster) — individual stars resolved live, with Live GPU Enhancement Controls (temporal + spatial denoise, non-linear contrast stretch) enabled, straight off the ASI678MC's live feed with no post-processing:
▶ Watch the live-view recording (49s, 3018×1902)
The two .mov recordings above are hosted as release assets rather than checked into the repository directly — they're well over GitHub's 100MB per-file limit for a normal git push.
Technical details — project layout, rendering/threading architecture, and the
non-obvious design decisions behind them — live in docs/:
docs/architecture.md— what's in each part of the codebase.docs/design-notes.md— decisions and gotchas worth knowing before changing the capture/rendering pipeline.docs/features.md— the current feature set in detail.
See .github/CONTRIBUTING.md for how to report
bugs, propose features, and submit code — including how new non-trivial
features go through spec-driven development (see
specs/README.md for how that works). This project
follows the Contributor Covenant. See
.github/SECURITY.md to report a vulnerability
privately, and .github/SUPPORT.md for where to ask
questions.
GPLv3 — see LICENSE.md, including the additional permission
(GPLv3 §7) that specifically allows linking this GPLv3 code against
closed-source camera driver SDKs. The vendored ZWO ASI Camera SDK under
Vendor/ZWO/ (ASICamera2.h, libASICamera2.dylib) is proprietary
third-party software, © ZWO Co., Ltd., under its own SDK terms, used here
under that permission. The bundled Messier/Caldwell/bright-star catalog
(skyformac/Resources/SkyCatalog/) is a small extracted subset of the
Stellarium project's own DSO catalog and
object-name data (GPLv2) — see THIRD_PARTY_NOTICES.md
for both full notices.