PSF Guard is an astrophotography image catalog manager with optional N.I.N.A. and Target Scheduler integration. You can catalog your FITS files in place, browse and grade frames by target, session, and filter, and automatically flag clouds, obstructions, tracking loss, and bad pointing. You can then preview stacks and export the accepted frames.
More from us: seiza.fyi — live plate solving in your browser, plus desktop apps for FITS browsing. Want live notifications while you image? Chatstronomy watches your N.I.N.A. rigs and posts captures, autofocus results, and status to Discord or Matrix.
Traditional metrics like star count and HFR can miss low-quality frames. In a test session, a tree line blocking the field left star counts within normal variation, and the HFR remained flat until the frame was more than 60% occluded. A thin cloud veil reduced star brightness by 37%, but the frame was still accepted by conventional grading. PSF Guard uses local, photometric, and temporal statistics calibrated on real sessions to detect these issues.
Build a catalog from FITS folders or open an existing Target Scheduler database. Browse by target, session, filter, date, and grade while the source files stay in place.
You can use the same grader user interface in the desktop app or any web browser. It provides auto-stretched previews, synchronized side-by-side comparison zoom and pan, batch operations, keyboard shortcuts, and full undo/redo support.
PSF Guard uses spatial metrics, cross-frame photometry, and plate-solving to detect occlusion, clouds, thin veils, errant light, off-target pointing, and tracking loss. The system provides the specific analysis and evidence for every grade.
The application displays expected catalog objects from coordinate metadata, solves image pixels on demand using the Seiza engine, and overlays object labels, outlines, an RA/Dec grid, and the measured center offset.
You can register and stack the accepted frames for each channel, then combine them into LRGB or narrowband (SHO, HOO, Foraxx) color previews. The preview tool includes background extraction, optional deconvolution, and linear FITS download features.
You can open a Target Scheduler database directly or synchronize state with a separate telescope computer. Recording your grades keeps the scheduler's acquired-image count accurate so it can replace rejected frames.
You can build a catalog from FITS folders. The application reads image headers to organize projects, coordinates, and plans, then processes the pixel quality data in the background.
The application moves rejected frames and their sidecar files out of the directory tree used by your stacking software. This process is documented, idempotent, and reversible, ensuring that restoring files never overwrites existing data.
You can synchronize projects, captured images, and grades between the telescope database and your local grading machine. This allows you to pull recent data, grade the frames locally, and push the results back.
The software includes star detectors ported from N.I.N.A. and HocusFocus, which feature Gaussian and Moffat PSF fitting, annotated star maps, and residual visualizations.
Image headers provide immediate coordinate context. If a frame lacks
embedded WCS data, selecting Solve field or pressing O
triggers a fast hinted plate solve. The system can fall back to a local blind index
if installed, caches the solution, and displays the shared Seiza overlay.
You can view flagged frames as annotated diagnostics. The application overlays the analysis grid on the image, highlights the cells where quality thresholds were breached, and provides the specific verdict and metrics in the caption to explain why the frame was flagged.
You can generate live-stack previews of your accepted frames directly in the grader. The application stacks cached channels into LRGB or narrowband color images using Seiza background extraction, custom stretch options, and optional deconvolution. Once verified, you can export the accepted light frames into folders structured for PixInsight WBPP, download them as a ZIP archive, or generate local hard links.
PSF Guard is available as a desktop app, Docker container, standalone binary, or Fedora RPM to support different environments.
The application has native installers for Windows, macOS (Apple Silicon), and Linux (Debian packages or AppImage).
You can run the application in Docker on NAS devices or home servers. The catalog directory mount must be writable to save grades and plans.
docker run -d -p 3000:3000 \
-v /path/to/catalog.sqlite:/data/database.sqlite \
-v /path/to/images:/images:ro \
ghcr.io/theatrus/psf-guard:latestThe standalone command-line binary runs on servers or within automated scripts, allowing you to screen entire imaging sessions in a single command.
psf-guard screen-fits ./LIGHT --annotate ./diag
psf-guard server catalog.sqlite ./imagesPrebuilt RPM packages are available for Fedora, and they include a systemd service unit to run the grader as a background daemon.
sudo dnf install ./psf-guard-*.x86_64.rpmMore projects from theatr.us