seiza-cli

The seiza command-line tool: star detection, hinted and blind plate solving, and star/object dataset management for astrophotography. The library lives in the seiza crate.

Install

Windows

Download the x86-64 MSI from the latest GitHub release. The installer supports all-users and current-user installs, adds seiza to PATH by default, and can launch the guided catalog setup when installation finishes. All-users installs place catalogs in the shared %ProgramData%\Seiza\catalogs directory; current-user installs use the user's local application-data directory.

A portable x86-64 ZIP is available on the same release page. See the Windows installer documentation for feature selection, unattended installation, and catalog-directory details.

Cargo

cargo install seiza-cli

Solving

# Hinted: approximate center (or FITS RA/DEC headers) plus pixel scale.
# --data takes a catalog file or a directory of catalogs; after
# `seiza setup` it can be omitted entirely.
seiza solve image.jpg --data data --ra 324.8 --dec 57.5 --scale 2.8
seiza solve light.fits --scale 1.45

# Blind: no position, just a plausible scale range. A directory supplies
# the deepest catalog and the blind index automatically.
seiza solve-blind image.jpg --data data --min-scale 0.5 --max-scale 15

# JPEG: inspect EXIF and solve a wide field without a pointing hint.
seiza image-info phone.jpg
seiza solve-blind phone.jpg --data data --sip-order 2 \
  --annotate solved.png --wcs solved.wcs

# A labelled chart: constellation figures, named stars, deep-sky objects,
# with marks on the ground below the horizon left out
seiza solve-blind phone.jpg --data data --sip-order 2 --sky-map sky-map.png \
  --sky-map-foreground

# Annotate detections or list objects in a solved field
seiza detect image.jpg --annotate out.png
seiza solve image.jpg --data data ... --objects data

# Predict tracks for one exposure from a cached current OMM set, or from an
# offline/historical OMM JSON or TLE file. FITS supplies time and OBSGEO when
# present; explicit metadata is also accepted.
seiza solve light.fits --scale 1.45 --satellites-celestrak --annotate tracks.png
seiza solve light.fits --scale 1.45 --satellites elements.json \
  --time 2026-07-18T08:30:00Z --exposure-seconds 30 \
  --observer-lat 37.3 --observer-lon -122.0 --observer-alt-m 50

# Query objects when sky bounds are already known; no image or solve needed
seiza catalog objects --data data --ra 10.6848 --dec 41.2691 --radius 3
seiza catalog objects --data data \
  --corner 8.91,42.14 --corner 12.47,42.02 \
  --corner 12.31,40.35 --corner 9.02,40.46 \
  --sort prominence --format json

# Resolve exact IDs/names or complete names; no image, solve, or network needed
seiza catalog object --data data "M 31"
seiza catalog object --data data "openngc:NGC224"
seiza catalog object --data data "andro" --prefix --limit 10
seiza catalog star --data data "TYC 5949-2777-1" --format json
seiza catalog star --data data "HIP 32349"
seiza catalog star --data data "RR Lyr"
seiza catalog star --data data "STF 2382 AB"
seiza catalog star --data data "RR L" --prefix --limit 10

Explicit file paths still work everywhere a directory is shown, for custom-built catalogs or unusual layouts.

JPEG metadata and pixel coordinates

Raster inputs are decoded and EXIF Orientation is applied once, including mirrors and the four transforms that swap width and height. Every command that reads a JPEG, PNG or TIFF does this, including the ASTAP and solve-field drop-ins and the JSON-RPC worker, and so do the C API and the desktop apps built on it: detection, solving, annotations, previews and exported WCS all use the same upright pixels. WCS pixel coordinates in the library are zero-based; the FITS WCS export uses FITS' one-based CRPIX convention. Apply the source Orientation before overlaying an exported WCS on the original JPEG. Annotated PNGs contain already-oriented pixels and must not be rotated a second time.

image-info emits JSON containing original/oriented dimensions, the applied transform and optional EXIF fields: camera, acquisition timestamp, subseconds, timezone offset, GPS position/altitude, heading and focal length. It recognizes the file type from its content, not its name, and declines FITS and XISF, whose headers carry this instead. Subseconds retain leading zeros. The UTC acquisition time comes from DateTimeOriginal with OffsetTimeOriginal, or else from the GPS date and time stamps, which are UTC by definition (capture_time_source says which); the machine's timezone is never assumed. An explicit solve --time overrides the EXIF acquisition hint used for minor bodies. Missing/malformed EXIF fields remain optional and do not prevent a stellar solve.

When solve-blind scale bounds are omitted and a valid 35mm-equivalent focal length is present, the CLI estimates central angular scale from the decoded image diagonal and first searches between half and twice that estimate. The estimate assumes the image is the camera's whole frame, so a crop or a phone held to an eyepiece can fall outside it; when that first search finds nothing, solve-blind searches again from 0.1"/px up to the estimate's coarse end. Each explicit --min-scale / --max-scale holds in both searches, and a hint bound that conflicts with an explicit one is dropped. Without this metadata the previous 0.1–20 arcsec/px defaults apply. SIP remains opt-in; compare residuals with and without it.

An iPhone main-camera frame (24 mm equivalent, from #210) solved blind at 71″/px, with detections in green and Gaia stars in red:

The same frame cropped to its central 1344×1008 pixels makes the focal-length estimate three times too coarse; the first search misses and the wide retry solves it at 72″/px:

pixel-scale search: 110.669–442.677"/px (EXIF equivalent focal length; explicit bounds override)
600 stars detected in 1344x1008 image
no solution in the EXIF focal-length range; retrying 0.100–442.677"/px
Blind-solved in 2.02s:
  center     : 03h 19m 42.05s +70° 56′ 13.5″  (49.92521°, 70.93708°)
  pixel scale: 72.0169"/px
  quality    : 106 stars matched, RMS 116.265"

--annotate on solve and solve-blind circles detected stars (green) and catalog stars (red). Fields wider than 10° across the diagonal, such as phone and camera-lens frames, get small markers and up to 600 catalog stars; narrower telescope fields get larger markers and 300 stars. Annotated images, like sky maps, are pictures to look at: FITS and XISF input is drawn from an automatic display stretch, in colour when the file has colour, whatever --detection-backend the solve used.

Sky map

--sky-map <out.png> on solve and solve-blind writes a chart of the solved image (EXIF-oriented, as loaded) for sharing. FITS and XISF images get an automatic display stretch, in colour when the file has colour:

• constellation stick figures (light blue) and constellation names;
• stars with IAU proper names down to magnitude 4.5 (gold), plus figure stars of magnitude 3 or brighter without one, by Bayer designation ("Gamma Cas", "Eta Cen"); the brightest 28 get labels;
• the 14 most prominent deep-sky objects (cyan), with common names, catalog ellipses for large ones, and "(edge)" when only the extent reaches the frame;
• a title bar, and a footer with matched stars, SIP order, pixel scale, RMS, field centre and the line-data credit.

Labels go where they overlap nothing placed before them, brightest stars first, and are dropped when nowhere fits. --sky-map-width sets the width, from 640 to 12000 pixels (default 2100).

--sky-map-foreground is for a photo with a horizon, trees or buildings in it: marks below the lowest detected stars that a catalog star confirms are left out, and figure lines fade there. It looks only at fields over 10° across, and only where the stars stop well short of the bottom of the frame across several neighbouring columns, so a frame with stars everywhere loses nothing. A named star the image shows is kept even below that line. The footer says when marks were left out.

Star names come from the star-identifier sidecar and objects from objects.bin, found next to --data or in the standard places (solve --objects picks the object file); without them the map still has the figures. Catalog marks show where things are, not that they were detected.

The figures are the Constellation Lines dataset by Marc van der Sluys (2005-2023), hemel.waarnemen.com. DOI: 10.5281/zenodo.10397192. Licensed under CC BY 4.0. Labels use the Inter typeface (SIL Open Font License 1.1, see fonts/).

EXIF Orientation is distinct from camera pointing. GPSImgDirection and its magnetic/true-north reference are reported but do not seed the solver; the stellar WCS determines pointing and rotation. HEIF and RAW/DNG decoding and multi-frame timing are not supported by this JPEG metadata path.

JPEG DateTimeOriginal and ExposureTime do not establish a continuous exposure. In particular, phone Night Sight/Night mode can combine many frames. Satellite overlays therefore still require explicit --time and --exposure-seconds describing one actual exposure; never pass a stack's total integration. JPEG GPS latitude/longitude can supply the observer position when both explicit coordinates are absent. Explicit coordinates take priority as a pair. EXIF GPS altitude is reported with its original reference and is not treated as ellipsoid height: supply --observer-alt-m when that height is known (otherwise the existing zero height default applies).

Star detection defaults to --detection-backend auto: decoded 8-bit images (including color JPEGs) and MTF-compressed FITS use the compact u8 pipeline, while other higher-precision images use f32. Pass --detection-backend f32 to retain fractional luma during an 8-bit solve or to detect directly from linear, native-precision FITS samples; pass --detection-backend u8 to explicitly quantize any input. The option is global and applies to detect, solve, solve-blind, and local worker solves.

Auto solves default to --detection-fallback f32. After an Auto/u8 solve miss, converted 8-bit color is redetected as f32 and FITS is reopened so detection can use its linear high-precision samples. --detection-fallback none disables the retry. Explicitly selected detection backends never fall back.

catalog objects accepts a cone or a convex polygon whose vertices are in boundary order. It can filter by object kind, magnitude, angular size, and common-name availability; results can be emitted as a table, JSON, or CSV. JSON and CSV include primary and alternate stable IDs, primary and contributing source provenance, aliases, and parent IDs when the catalog provides them. The prominence score is a catalog-based prediction, not proof that the object is visible in the image pixels.

catalog object resolves primary/common names, aliases, and stable or alternate IDs. Both object viewport queries and name completion use indices embedded in the memory-mapped objects.bin; normal open does not decode every record or touch every index page. Add --all-sources to audit every normalized upstream row, preferred facet selection, and source-qualified geometry.

Background extraction

Fit and remove a smooth background from a calibrated linear FITS or XISF image:

seiza background stack.fits --output corrected.fits \
  --model-output background.fits --diagnostics background.json

The default is a robust, per-channel quadratic surface with shared sample positions. Use --degree 1 for a conservative plane, --mode divide for a multiplicative field, and --border-fraction to keep sample windows away from registration edges. --sample-radius, --samples-per-axis, rejection sigmas, and refit count are available for controlled tuning.

Corrected and model outputs are linear 32-bit floating-point FITS and preserve a valid input WCS. The JSON diagnostics include coefficients, reference levels, sample positions, weights, and rejection reasons. The input, corrected output, model, and diagnostics must be distinct paths. Raw Bayer mosaics are rejected because fitting the interleaved CFA colors as one channel would create a false surface; debayer or stack them first.

Photometric colour calibration

Calibrate a linear RGB stack's colour against Gaia DR3 star colours:

seiza color-calibrate stack.fits --output stack-cc.fits --report colour.json

The image needs an astrometric solution: FITS WCS cards, which seiza stack keeps from the reference frame, or the AstrometricSolution properties PixInsight writes into XISF files. A PixInsight solution's distortion layers have no TAN-SIP equivalent and are left out, which moves stars near the corners of a distorted field by a few pixels; the photometry finds them anyway. Seiza reads Gaia DR3 photometry from an offline catalog when one is installed (stars-gaia-photometry.bin in a catalog directory, or --gaia-catalog). Otherwise it fetches the field from ESA's Gaia archive, or from GAVO's mirror when ESA's fails, and caches it (--gaia-cache); a CSV you supply also works (--gaia-csv). It measures every isolated, unsaturated Gaia star in R, G and B, fits each instrumental colour against Gaia BP−RP, and sets the gains that render a star of the white reference's colour neutral: the Sun's (BP−RP 0.82) unless --white-bp-rp says otherwise. No filter or sensor curves are needed; the stars measure the camera's own response. Background neutralization then gives the sky the same level in every channel (--no-background-neutralization leaves it).

On the 126-frame M45 stack (ASI2600MC, 173 mm), about 1,670 isolated Gaia stars brighter than G 13 calibrated it, with 0.044 and 0.032 mag of scatter about the red and blue colour fits. PixInsight's SPCC, given the same image and a G2V white reference, chose a red gain 4.8% lower and a blue gain 3.2% higher. The colour model is not the cause: on the stars both tools measured, SPCC's filter-curve method and Seiza's BP−RP fit agree within 0.7% when given the same fluxes. The fluxes differ instead. For 60 isolated stars SPCC's PSF photometry reports R/G 0.712, while apertures from 4 to 36 px all give 0.667–0.697.

The offline catalog is built from Gaia DR3 itself (CC BY-SA 3.0 IGO), not from PixInsight's databases. Seiza hosts a prebuilt copy (about 460 MB, downloaded zstd-compressed) that is not part of the standard bundle; install it with setup or by name:

seiza setup --preset solver-lite --gaia-photometry
seiza download-data prebuilt --output data --file stars-gaia-photometry.bin

To build it yourself, scripts/build-gaia-photometry.sh downloads G, BP, RP and RUWE for every source to G 15 in 768 resumable chunks and builds the catalog, about 470 MB; it takes a few hours and can run unattended. Copy the result into Seiza's catalog directory ($SEIZA_CATALOG_DIR, or ~/.local/share/seiza/catalogs on Linux) or pass it with --gaia-catalog:

ARCHIVE=gavo nohup scripts/build-gaia-photometry.sh ~/gaia-photometry > gaia.log 2>&1 &
cp ~/gaia-photometry/stars-gaia-photometry.bin ~/.local/share/seiza/catalogs/

The two steps are also available on their own: seiza download-data gaia-photometry --output chunks [--archive esa|gavo] and seiza build-data gaia-photometry --input chunks --output stars-gaia-photometry.bin.

Light deconvolution (experimental)

seiza deconvolve applies a conservative damped Richardson-Lucy pass to a calibrated or stacked linear mono/RGB FITS/XISF image. Measure the FWHM of several unsaturated stars in pixels and use their median as the explicit Gaussian PSF:

seiza deconvolve stack-bg.fits --output stack-light-dc.fits \
  --psf-fwhm 3.1 --iterations 4 --amount 0.35 --noise-fraction 0.001

Run this after calibration, stacking, and background correction and before a display stretch. Start with 3-5 iterations and a 0.25-0.4 blend. Compare input and output with the same stretch, paying particular attention to bright-star rings, background noise, and image borders. Raw Bayer mosaics are rejected; debayer or stack them first. Missing registration borders marked with NaN stay masked in the output.

This prototype uses one circular Gaussian PSF across the whole field. It does not infer detail, estimate a spatially varying PSF, or replace a model-based restoration workflow. See the deconvolution design note for the algorithm, guardrails, and next experiments. Four real-corpus comparisons record the first measured trial, and the model-based restoration plan defines a safer path from synthetic degradations and expert before/after pairs to a provenance-bearing learned operation.

Image stacking

seiza stack calibrates, registers, and incrementally integrates FITS or XISF light frames onto the reference frame's fixed output grid:

seiza stack light-001.fits light-002.fits light-003.fits \
  --output stack.fits --preview stack.png --report stack-report.json

seiza stack lights/*.fits --output stack.fits \
  --bias master-bias.fits --dark master-dark.fits --flat master-flat.fits \
  --reintegrate --max-registration-drift 256 \
  --max-registration-drift-fraction 0.15 --min-overlap 0.60

Defaults and quality options

The defaults aim for the best result from a night of frames; each step can be changed:

Option	Default	What it does
--reference auto|first	auto	auto scores every frame on a half-resolution view (star signal over sky noise, which seeing, trailing, haze and twilight all lower) and, among frames near the best score, takes the flattest sky. first keeps the first frame given.
--registration-model similarity|affine|quadratic	quadratic	After the similarity match, fit a polynomial to up to 2 000 stars to follow lens distortion. A frame with too few stars keeps its similarity.
--normalization none|global|local|local-background	local-background	local-background keeps one gain per channel, measured from star photometry, and matches each tile's background to the reference's, so frames whose sky gradients differ leave no seams where coverage changes. local also fits a gain per tile.
--local-tile-size	256	Tile size for local and local-background.
--weighting equal|inverse-noise	inverse-noise	Weight each frame by the inverse of its noise variance relative to the reference, so hazy frames count for less.
--interpolation bilinear|lanczos3	lanczos3	Lanczos-3 resampling, with PixInsight-style clamping against ringing; sharper, at about twice the resampling cost.
--demosaic vng|mhc|bilinear	vng	Bayer frames: VNG keeps each star's colour across its profile; MHC gives slightly sharper stars but rings around small ones; bilinear is fastest and softest. All three balance the mosaic's channels first.
--bayer-drizzle	off	Integrate each Bayer frame's photosites without demosaicing, on the reference grid; pays off on well-dithered data. Not the same as --drizzle.
--reintegrate	off	After stacking, read every admitted frame three more times and integrate with leave-one-out rejection. This removes trails in the first frames, which online rejection cannot revisit, and refits each frame's background against an integration of the best twenty.
--scratch-directory <PATH>	output's directory	Where --reintegrate keeps each prepared frame between passes, so it calibrates, demosaics and resamples each frame once instead of three times. It needs 4 bytes per pixel per channel for every frame, about 39 GB for 126 ASI2600MC frames, and deletes them when done; a frame that does not fit is prepared afresh each pass.
--drizzle 1|2|3|4	off	Drizzle the stack onto a grid this many times finer than the reference, as WBPP's DrizzleIntegration does. Turns on --reintegrate, whose rejection decides which pixels each frame drops. The output is the drizzled image with the reference WCS scaled to it. Bayer frames drop each photosite into its own colour, with no demosaicing. 2 recovers detail in undersampled, well-dithered data.
--drizzle-drop-shrink	0.9 mono, 1.0 Bayer	Each drop's side as a fraction of a source pixel. Smaller drops keep more detail and need more dithered frames to fill the grid.
--workers, --pipeline-memory-mib	derived, 4096	Frames read and prepared at once, and the memory for them.

On 126 one-shot-color frames of M45 (ASI2600MC, 173 mm, no calibration) the defaults stacked in 2 min 23 s at 2.7px FWHM with a 0.10px red-blue offset; the settings before these options took 3 min 16 s at 3.1px and 0.42px. Adding --reintegrate took 5 min 44 s, and --drizzle 1 6 min 58 s at 2.69px FWHM and an SNR of 356. After WBPP had registered the same frames, PixInsight's ImageIntegration and DrizzleIntegration took 6 min 54 s and 2 min 41 s for 2.67px and 357. On 62 undersampled H-alpha frames (ASI2600MM, 300 mm), --drizzle 2 took 1 min 23 s in all and gave 1.78px FWHM in reference pixels; WBPP's whole run with 2x drizzle took 7 min 5 s for 1.77px.

Raw calibration sequences can be integrated into reusable masters first:

seiza master bias bias/*.fits --output master-bias.fits --report master-bias.json
seiza master dark dark/*.fits --bias master-bias.fits \
  --output master-dark.fits --report master-dark.json
seiza master flat flats/*.fits --bias master-bias.fits \
  --dark-flat master-dark-flat.fits --output master-flat.fits \
  --report master-flat.json

Bias and dark construction uses a two-pass, leave-one-out sigma-clipped mean. Flat construction calibrates and normalizes each input once, then uses a scratch-backed temporal median/MAD sigma-clipped mean. This improves rejection of moving stars that overlap a sensor pixel in multiple sky flats without aligning the stars or smoothing the sensor response. Two-frame sets are averaged without rejection, regardless of master kind. More frames and enough star motion are needed to distinguish stars from persistent flat response. Faint halos can remain in small or noisy sets even with a clean majority; saturated or other contamination present in most inputs can be retained more strongly.

Flat scratch storage uses OS temp and needs about four bytes per input sample; tile memory is bounded at 64 MiB in addition to the image and master buffers. The temporary file is removed after completion, cancellation, or failure. Dimensions, channels, CFA layout, and available camera, binning, gain, offset, temperature, filter, and dark-exposure metadata are checked before incompatible frames can be mixed. The completion message and JSON configuration report the actual integration and rejection method. The rereads_inputs field describes source pixel reads during integration (not the separate SHA-256 provenance pass): false for flats, true for bias/dark. An all-rejected flat pixel falls back to its temporal median; bias/dark pixels use the unclipped mean. Both the report and warning identify that fallback. The report's inputs contains only the combined frames with their own sample counts; skipped_inputs retains the identity and reason for every excluded frame, so a metadata mismatch cannot shift another frame's statistics.

Calibration, registration, normalization, online delta-sigma rejection, and integration all operate on linear f32 samples. --preview is an optional display-only stretch and never feeds pixels back into the stack. Incoming frames are admitted atomically: incompatible images, weak registrations, excess transform drift, low overlap, or implausible normalization leave the existing additive stack unchanged. The optional --report JSON records SHA-256 identities for every source and calibration master, the complete configuration, and the ordered accepted/rejected disposition ledger. The reference is always integrated, so it counts toward accepted_frames but has no entry in the per-frame frames ledger; that ledger lists only the frames pushed after it, with each one's weight when frames are weighted. FITS and report outputs are published atomically after they are complete.

Mono inputs produce a one-plane linear FITS stack. Three-plane FITS/XISF inputs remain RGB, while raw one-shot-color frames with BAYERPAT are calibrated in their native CFA sampling before demosaicing. Star detection uses a temporary luminance view, but registration is applied to all three channels and normalization is estimated per channel. The output is an unstretched three-plane float32 RGB FITS; --preview writes an RGB display stretch.

The registration search is explicitly bounded at the center of the reference frame. Its effective default is whichever is larger: 256 pixels or 15% of the reference frame's larger dimension. Configure those components with --max-registration-drift and --max-registration-drift-fraction. Increase either for a sequence with larger dithers or crop-origin offsets; lower values make the expected motion constraint tighter. Set the fractional component to zero when a strict pixel-only limit is desired. Light frames may have different dimensions: valid samples are mapped onto the reference frame's fixed grid, pixels outside a source crop remain masked, and --min-overlap controls how much usable overlap is required for admission.

Meridian-flipped frames are handled automatically. The default 10-degree rotation gate measures deviation from the nearer of the reference orientation and its 180-degree counterpart, so a measured transform of 179.3 degrees has a 0.7-degree admission deviation. The complete measured transform—not a header flag—is then used to rotate and resample the incoming pixels onto the reference grid before normalization and integration. Accepted-frame diagnostics and the JSON report retain the full measured rotation.

--flat accepts an integrated master flat in the light frame's raw sampling. For legacy masters, --bias removes the flat's pedestal before normalization. Masters built by seiza master carry FITS calibration-state headers, so a bias-subtracted dark or calibrated flat is not subtracted twice. Planar RGB flats are normalized independently per channel. CFA flats remain one-channel and are applied before debayering. See the stacking design for the live API, rejection semantics, and PSF Guard integration boundary.

Color composition

seiza color consumes mono float32 FITS stacks. It can emit an RGB FITS, a quick-look PNG, or both:

seiza color rgb --red r.fits --green g.fits --blue b.fits \
  --output rgb.fits --preview rgb.png

seiza color lrgb --luminance l.fits --red r.fits --green g.fits --blue b.fits \
  --luminance-weight 1.0 --output lrgb.fits --preview lrgb.png

seiza color lrgb --luminance l.fits --red r.fits --green g.fits --blue b.fits \
  --luminance-mode super --output super-lrgb.fits --preview super-lrgb.png

seiza color narrowband --ha ha.fits --oiii oiii.fits --sii sii.fits \
  --palette sho --output sho.fits --preview sho.png

seiza color narrowband --ha ha.fits --oiii oiii.fits \
  --palette foraxx-hoo --preview foraxx-hoo.png

Direct palettes are sho, soh, hso, hos, osh, ohs, and hoo. Dynamic palettes are foraxx-sho and foraxx-hoo. The default independent 0.1%/99.5% percentile scaling is intended for fast visual matching; use --normalization none for masters whose backgrounds and scales are already matched. Foraxx additionally requires those unnormalized samples to lie in [0, 1]; keep the default percentile mode for sensor-unit masters. Foraxx working channels use a median/MAD midtones transfer; tune it with --foraxx-target-median and --foraxx-shadows-clip.

LRGB defaults to linear luminance replacement. --luminance-mode super instead sets the target luminance to L + R + G + B after normalization while preserving RGB chromaticity. Its linear output may exceed one. --luminance-weight applies only to replacement mode. color rgb accepts the same flag: --luminance-mode super scales the triplet to a synthetic R + G + B luminance with no luminance stack, marked SEIZACLR='SUPER-RGB'.

Linear RGB/LRGB, super-LRGB, super-RGB, and direct-palette FITS files carry SEIZATRF='LINEAR'. Foraxx follows its published stretched-channel formula and carries SEIZATRF='DISPLAY'; previews therefore do not pretend it is a linear stack. Input dimensions and path roles are validated, and WCS comes from the command's reference channel. See the color-composition design.

By default, non-reference filter stacks are star-registered and resampled onto L for LRGB, R for RGB, or H-alpha for narrowband. The command reports matched stars, RMS, drift, and rotation, rejects RMS above 2 pixels, and uses the normal 256-pixel-or-15% drift bound. Configure those gates with --max-registration-rms, --max-registration-drift, and --max-registration-drift-fraction; use --no-register for masters already registered to the same reference.

Persistent worker

Applications performing repeated solves can keep a catalog and blind index open behind a newline-delimited JSON-RPC 2.0 process:

seiza worker --data data --index data

The same protocol can adapt local image paths to a queued seiza-server (self-hosted, or the hosted instance at seiza.fyi):

seiza worker --server http://solver-host:8080

Remote mode defaults to a compact grayscale PNG upload. Use --server-upload fits to stream the original FITS file and preserve headers, or --server-timeout SECONDS to change the default five-minute deadline. Bearer authentication uses --server-token or SEIZA_SERVER_TOKEN. See the versioned wire contract for request and response details.

Use with N.I.N.A.

seiza speaks ASTAP's CLI contract: set N.I.N.A.'s plate solver to ASTAP and point the ASTAP path at the seiza binary (a copy named astap.exe also works). On Windows, use the Seiza Catalog Setup Start-menu shortcut installed by the MSI; on every platform, seiza setup installs a usable selection into a directory ASTAP mode discovers automatically. For a manual layout, run seiza download-data prebuilt --output <directory> and point SEIZA_CATALOG_DIR at that directory. Advanced SEIZA_STAR_DATA and SEIZA_BLIND_INDEX file-or-directory overrides remain available. Hinted and blind-slot solving both work; see the ASTAP-compatible mode design.

Use with Siril

seiza also speaks astrometry.net's solve-field CLI contract, and answers Siril's Windows bin/bash launch wrapper itself (no cygwin needed). Run seiza install-solve-field --dir <dir>, point Siril's astrometry.net directory preference at that directory, and Siril's normal astrometry.net solving works unchanged, including SIP distortion orders. Catalogs resolve the same way as ASTAP mode. Siril reports PSF amplitudes rather than photometric flux, so seiza automatically re-measures star flux from the source image next to the star table when present — see the solve-field mode design for details.

Datasets

The quickest route is the prebuilt, SHA-256-verified set hosted at downloads.seiza.fyi (Tycho-2 and Gaia solver tiles, the blind index, the unified object catalog, minor bodies, the Tycho/Bright Star/GCVS/WDS/IAU identifier sidecar, and a nightly-refreshed transient list):

# Running this by itself prints the recommended prebuilt and setup routes:
seiza download-data

seiza download-data prebuilt --output data
seiza download-data prebuilt --output data --file objects.bin --file transients.bin
# The optional ~9 GB Gaia G≤20 catalog is explicit; pair it with the blind index
# for deep blind solving.
seiza download-data prebuilt --output data \
  --file stars-deep-gaia20.bin --file blind-gaia16.idx
# The optional Gaia photometry catalog for colour calibration is explicit too.
seiza download-data prebuilt --output data --file stars-gaia-photometry.bin

The other download-data subcommands acquire upstream source material for custom catalog builds; they are not required for normal Seiza use.

Historical satellite elements use the same resolver as applications: a nearby entry in the durable cache first, then the rolling Seiza mirror, with IAU SatChecker as the on-demand fallback. Operators can prewarm one or more epochs without teaching an application which provider to call:

seiza download-data satellite-history \
  --epoch 2025-10-17T12:00:00Z 2025-10-18T12:00:00Z \
  --cache /var/lib/seiza/satellite-mirror/cache

seiza build-data satellite-manifest converts that cache into a validated, content-addressed publication tree. The complete cron, S3 publication order, backfill, retention, and public verification procedure is in the satellite mirror runbook. The mirror publisher uses --origin so its scheduled bucket is fetched from IAU SatChecker rather than resolved from the mirror it is updating.

For an interactive selection, run seiza setup. This is also the command offered by the Windows installer. It presents lightweight, Gaia, deep-blind, optional G≤20, and every-catalog presets, then delegates to the same verified prebuilt downloader. Every preset includes object search, Solar System objects, and active transients.

The downloader reads one standard bundle from /data/v4/manifest.json and caches its immutable, content-addressed files by SHA-256 before copying the requested selection into the same flat local output directory. The shared platform cache can be overridden with SEIZA_CACHE_DIR. The optional G≤20 catalog is hosted alongside the bundle but is never included in a bare download-data prebuilt; name it with --file or choose the relevant setup preset. It never combines catalogs from different hosted bundle versions. Previously released /data/ and /data/v2/ paths remain frozen for classic v1 and v0.4.1/v0.5 readers. The historical /data/v3/ probe used by v0.4.0 remains reserved and may be absent; those readers retain their existing fallback behavior.

Library integrations can use seiza-download directly for async, automatic cache management. The raw catalog commands below are implemented by the separate seiza-sources crate so applications do not inherit Gaia/VizieR/MPC source-acquisition behavior.

Building from primary sources stays supported for custom depths, epochs, or tile granularity — note the Gaia TAP download alone can take many hours:

seiza download-data tycho2 --output raw/tycho2
seiza download-data star-identifiers --output raw/star-identifiers
seiza build-data tycho2 --input raw/tycho2 --output stars-lite.bin \
  --identifier-index stars-lite.ids.bin \
  --identifier-sources raw/star-identifiers

seiza download-data gaia --output raw/gaia        # Gaia DR3 via TAP, resumable
seiza build-data gaia --input raw/gaia --output stars-gaia.bin

seiza download-data objects --output raw/objects
seiza download-data curation --output raw/curation --commit <git-sha>
seiza build-data objects --input raw/objects --output objects.bin \
  --curation-dir raw/curation \
  --source-manifest objects.sources.json
seiza download-data transients --output raw/transients
seiza build-data transients --input raw/transients --output transients.bin
seiza download-data mpc --output raw/minor-bodies
seiza build-data minor-bodies --input raw/minor-bodies --output minor-bodies.bin

The optional curation directory is a pinned local checkout; the builder never fetches it. Its curation.json records repository, commit, and schema version. Each objects/<id>.toml file owns the corrections, relations, selections, exceptional outline remappings, notes, and structured evidence for one canonical target. Normally named OpenNGC outlines are associated directly during upstream ingestion and do not require curation documents. The optional source manifest records the output hash and size, metadata coverage counts, source URLs, curation revision, and hashes of every raw catalog and curation file used. The optional identifier sidecar provides memory-mapped exact TYC/HIP/HR/HD/ SAO/FK5 lookup plus exact and prefix search over IAU proper names, Bayer/Flamsteed names, GCVS variables, and WDS double-star designations. It does not change the solver's compact star tile file.

To publish new transient and Solar-system data without rebuilding the object or star catalogs, put only the replacement transients.bin and minor-bodies.bin in a directory and roll forward each complete manifest:

seiza build-data manifest --dir next-dynamic \
  --base-manifest current-v2.json \
  --version catalog-bundle-v2-YYYY-MM-DD --output next-v2.json
seiza build-data manifest --dir next-dynamic \
  --base-manifest current-v4.json \
  --version catalog-bundle-v4-YYYY-MM-DD --output next-v4.json \
  --artifact-dir next-v4-artifacts

The v2 output retains flat keys for released v3-object readers. The v4 output uses content-addressed artifact keys and stages both uncompressed and maximum-compression zstd artifacts in one upload-ready tree. The manifest retains the uncompressed artifact for old v4 readers; new readers stream-decompress into the normal uncompressed mmap cache. Both commands require the resulting bundle to contain every required catalog.

Normal catalog opens do not perform exhaustive validation. Validate any seiza star tile, identifier sidecar, blind index, object catalog, or minor-body catalog explicitly when required; the file format is auto-detected:

seiza catalog validate --data stars-lite.ids.bin
seiza catalog validate --data stars-lite.bin
seiza catalog validate --data objects.bin

FITS and XISF files are read natively through seiza-fits and seiza-xisf. Both provide typed linear pixels, an automatic MTF stretch for u8 detection and previews, a linear normalized representation for f32 detection, and RA/DEC hints from FITS-compatible metadata. PNG, JPEG, and TIFF continue to use the Rust image decoders. Commands that save linear images write FITS by default and monolithic Float32 XISF when the output path ends in .xisf.

Parameterized display stretching

seiza stretch applies an explicit reusable seiza-stretch model to a linear mono or RGB FITS/XISF image and writes a display-referred PNG, JPEG, or TIFF:

seiza stretch stack.fits --output preview.png percentile-asinh \
  --black-percentile 0.01 --white-percentile 0.995 --strength 10

seiza stretch stack.fits --output preview.png auto-mtf \
  --target-median 0.2 --shadows-clip -2.8

seiza stretch color.fits --output preview.png \
  --color-strategy luminance-preserving asinh \
  --black 0 --white 1 --strength 8

seiza stretch stack.fits --output preview.png ghs \
  --stretch-factor 4 --local-intensity -1 --symmetry-point 0.35 \
  --protect-shadows 0.1 --protect-highlights 0.8

Other model subcommands are identity, linear, and explicit mtf. The ghs subcommand exposes the deterministic GHS parameters; informed automatic selection can be layered over it later. RGB may use linked, unlinked, or luminance-preserving analysis/application. Stretching is never applied to linear stack output unless this command or a library caller explicitly requests it. See the stretching design.

License

Apache-2.0