Mosaic Toolbox
Several filters of a mosaic, assembled onto one common grid in a single run.
Compatibility
Compatible with PixInsight 1.9.5
Tested and verified against the latest PixInsight release, 1.9.5 (Lockhart).
Overview
Assembling a multi-filter mosaic by hand means reprojecting every tile, filter by filter, hoping each run lands on the same grid, then joining the seams one at a time. Mosaic Toolbox does it all in a single pass.
It computes one common astrometric grid from every tile of every filter, reprojects each plate-solved tile onto it, erodes the soft reprojection edges, then joins the tiles photometrically: star flux ratios set the brightness scale, and a smoothed surface spline models the residual gradient.
Because every filter is written onto the same grid, the L, R, G, B, S, H and O outputs share identical coordinates, field of view and pixel dimensions: they combine straight away (ChannelCombination, PixelMath, LRGB, SHO), with no further registration. Autocrop, a screen auto-stretch and a full per-join history are included.
Self-contained: no other mosaic script is required. Inputs must be linear, plate solved and already corrected for gradients. Written by Nicolas Godingen, maintained by Caelo Works. Interface in English and French. Licensed CC BY-NC 4.0 (non-commercial use).
With thanks
Nicolas Godingen
Author of Mosaic Toolbox
Nicolas Godingen wrote Mosaic Toolbox, and the heart of it is his: the common grid, the reprojection, the photometric join and every default that makes an unattended multi-filter assembly come out right. He built it against his own mosaics, and it shows in the details a quicker tool would have skipped. Caelo Works is glad to carry it forward. Thank you, Nico.
Features
One common grid
The astrometric grid is computed from every tile of every filter at once, then each plate-solved tile is reprojected onto it. No more separate per-filter runs each landing on a slightly different grid.
Photometric join
Matched-star flux ratios (identical aperture, identical position) set the brightness scale, then a smoothed surface spline models the residual gradient. A pixel fallback covers a star-poor overlap, and says so.
Every channel aligned
L, R, G, B, S, H and O come out on the same grid, with identical coordinates, field of view and pixel dimensions. They combine straight away (ChannelCombination, PixelMath, LRGB, SHO), with no further registration.
Autocrop and auto-stretch
Autocrop trims to the largest rectangle where all channels hold data everywhere (no empty border, no black corners), computed once for every channel. A screen auto-stretch shows the result instead of a black frame, touching no pixel.
Full per-join history
Each mosaic carries a rebuilt astrometric solution and a full HISTORY of every join: scale factor and star count per channel, sample count, smoothness, taper length, join mode.
Self-contained and bilingual
No dependency: the photometric join engine is the script's own, nothing else to install. Interface in English and French, switched in place from the header (HISTORY entries stay in English).
Screenshots
Privacy, network and files
Network
Mosaic Toolbox makes no network connection and downloads nothing.
External programs
The only program it can start is your operating system's own URL handler (explorer.exe on Windows, open on macOS, xdg-open on Linux), and only when you click the "Caelo Works" link in the dialog header. It opens the product page in your default web browser, in the interface language: https://pixinsight-scripts.caelo.works/en/scripts/pix-mosaic-toolbox in English, https://pixinsight-scripts.caelo.works/scripts/pix-mosaic-toolbox in French. Both addresses are fixed in the script; nothing else is ever launched, and nothing is launched at any other time. The link's tooltip says the same thing.
Storage
Your choices are kept in the PixInsight settings, under the MosaicToolbox/ key, through PixInsight's own settings interface. The script writes no file to disk: the mosaics stay in PixInsight windows until you save them yourself, and the FITS keywords and astrometric solution it writes go only on those output windows.
The pixel data of your source images is never modified. If a source window carries its plate solution only as header keywords, pressing Run asks PixInsight to rebuild that solution from them, the same operation the core astrometry tools perform.
Data
No telemetry, no usage tracking, no personal data collected or sent.
Install
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01
Add the CaeloWorks repository
In PixInsight, open Resources → Updates → Manage Repositories and add the CaeloWorks repository URL:
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02
Check for updates
Run Resources → Updates → Check for Updates and accept: PixInsight downloads and installs the script.
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03
Restart PixInsight
Relaunch the application: the script shows up in the Script menu. Future updates then arrive automatically.
Once installed, the script shows up under Script → CaeloWorks → Mosaic Toolbox. Requires PixInsight 1.9.4+, Windows, macOS or Linux. Inputs must be linear, plate solved (ImageSolver) and already corrected for gradients. Written by Nicolas Godingen, distributed by Caelo Works under the CC BY-NC 4.0 licence (non-commercial use).
Changelog
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2.4.2 2026-10-13
The "Caelo Works" header link follows the interface language: the French product page for the French interface, the English one for the English interface. The address is read at click time, so a language switch is followed, and the tooltip shows the one that will open.
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2.4.1 2026-10-13
Brought in line with the CPD Program Rules v1.0 published by Pleiades Astrophoto, with no processing change: an assembled mosaic is identical to 2.4.0's. The "Caelo Works" header link opens the script's own page instead of the catalogue home; on Windows the browser is opened by explorer.exe directly rather than through the cmd shell, and a tooltip says it is the only program the script ever starts. The README gains a "Privacy, network and external programs" section, and now states exactly what happens to source windows. Verified compatible with PixInsight 1.9.5.
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2.4.0 2026-09-03
First release distributed by Caelo Works. The processing engine (common grid, reprojection, photometry, gradient model, join and per-channel assembly) is Nicolas Godingen's 2.3.1, carried over unchanged, so an assembled mosaic's pixels are identical. The changes are to the interface (a CaeloWorks-styled header, the language selector), the string catalogue, packaging and testing.