OSC Multi-Night Stacking — Siril 1.4 Python Application Script

Version 2.0

Overview

OSC Multi-Night Stacking is a Python + PyQt6 GUI Siril application script that automates the creation of Siril 1.4 scripts for multi-night deep-sky stacking projects using Siril-style directory layouts.
It provides a Sirilic-like interface using the new Siril Python API that is fully portable, written in Python, and designed for users who capture multiple nights of imaging data and want a one-click way to generate correct Siril processing pipelines.

**Note: Siril 1.4 or later is required **

✨ New Features (v2.0)

• The main feature that has been added in this version is mosaic pre-processing stacking.
  • Allows mosaic pre-processing and stacking of standard rows x columns grid layout panels that applications such as Nina generate.
  • Allows for adjustment of border feathering (px) or overlap (%).
  • Allows for selection of Global reference frame.
  • Drizzle per panel or the whole mosaic.
  • Allows for adjusting the canvas scale.
  • Automatic panel layout creation.
• Compression of drizzled intermediate fit images in now supported and enabled.

Limitations

• The mosaic feature is for traditional telescope configurations and NOT for smart telescope use. There are others tools and scripts for smart telescope mosaic processing.
• The mosaic functionality in Siril needs RA/DEC coordinates in the fit images in order to do platesolving. For this reason the script will more than likely not work with images that are generated by DSLR cameras.

✨ Bug Fixes and other enhancements (v1.2)

• Script now will use the Siril Python API by default to run the ssf script and not use siril-cli.
• Script will now default to the current Siril working directory when the script is started.
• Added Force siril-cli checkout to allow user to use siril-cli if they really want that. This allows the user to abort the ssf script within the OSC Multi-Night Stacking Python script.
• Added Quick start Instructions to the Help Menu
• Added various Tool Tips.

✨ New Features (v1.1)

New enhancements:

• Now compresses final register and stack fit files instead of just the intermediate session fit files.
  • Limitation: register and setapplyreg commands will not compress fit files if drizzling is enabled due to a limitation with Siril 1.4 where the drizzling functionality does not support compressed fit files.
• Added pack Sequences feature - this allows you to pack the fit or fz files into a SER or FITSEQ sequence file. This allows us to overcome the 2048 open file limit on Windows.
  • Off by default
  • Auto, FITSEQ, and SER are the options that can be used.
  • Pack Sequences only will pack LIGHT frames. LIGHT frame pack threshold is configurable and can be lowered and raised as needed.
  • Auto uses the FITSEQ sequence file format (recommended for maximum compatibility) where is puts the fit or fz files into into a single file for stacking.

✨ Features (v1.0)

Core Capabilities

• Multi-Night Project Handling

  • Supports OSC images.
  • Supports any number of nights of imaging under a single project root.
  • Ability to Create, Save, and Load Project json files.
  • Automatically merges registered and stacked data across nights.
  • Generates night-specific and global Siril script for calibration, registration, stacking, and post-processing.
  • Final stack copied, mirrored, and opened in Siril

• Automatic Directory Detection

  • Uses Siril style directory structure.
  • Detects camera name, gain, offset, binning, and exposure length from FITS headers for file naming.

• Script Generator for Siril 1.4

  • Produces fully commented .ssf scripts compatible with Siril 1.4 Beta 3/4.
  • Handles master bias/dark/flat creation automatically.
  • Adds mirrorx -bottomup at the final stage to correct FITS orientation.
  • Includes optional setcompress 0 for lossless FITS saving.
  • Drizzle: Scaling, Pixel Fraction, Kernel
  • 2-pass registration toggle
  • Global stacking options (sigma or winorized rejection (sigma high and low), mean)
  • 32-bit output for final stack

• UI Highlights

  • Qt-based tabbed interface for Project, Nights, and Processing Settings.
  • Live detection of unsaved project changes (with save prompt).
  • Configurable Siril executable path and project output root.
  • Abort Run button (graceful stop)

• Validation & Logging

  • Generates project-specific log files.
  • Siril console logging via sirilpy
  • Performs validation on missing calibration frames b=and bad paths.

---

🧭 Typical Directory Layout

ProjectRoot/

├─ Session 1/

│ ├─ process/

│ ├─ LIGHTS/

│ ├─ DARKS/

│ ├─ FLATS/

│ └─ BIASES/

├─ Session 2/

│ 

⚡ Quick-Start — Running from Siril 1.4

Use this 7-step guide to run the Multi-Night Stacking Python Application and process all of your sessions in Siril 1.4.

🧰 Requirements

• Siril 1.4 Beta 4 (with Python scripting enabled)
• Python 3.10 + with PyQt6, astropy, and sirilpy installed

---

🪄 Steps

1. Downlaod osc-multi-night-stacking.py

   • Place the script in your Siril Scripts directory.
   • Refer to the Siril 1.4 doc on how to set a Siril Scripts directoey.

2. Open Siril 1.4

   • Start Siril normally.
   • Ensure that the script is visiable in the UI. (Scripts->Python Scripts)
   • Refer to the Siril 1.4 Script doc if it is not.

3. Launch the Application Script from the Scripts -> Python Scripts menu in Siril

   • The OSC Multi-Night Stacking script GUI will open alongside Siril.

4. Create or Load a Project

   • Click New Project → choose your target root folder
   • Check or uncheck features and options
   • Add Sessions as needed
   • Add LIGHTS, FLATS, DARKS, BIAS frames to Sessions or Panels as needed
   • The app auto-detects all session folders (Session 1, Session 2, …) if they were previously created.
   • Check or uncheck features and options as needed

5. Prepare Working Directory (Symlink?copy Files)

   • Inside each Session X folder.
   • The application writes its .ssf script files into this folder and Siril uses it as the working directory.
   • Why: Siril reads and writes intermediate calibrated and registered FITS frames inside this directory.
   • Each session will therefore have:

     Session 1/process/
     Session 2/process/
     ...
     

6. Generate Siril Script

   • Confirm features and option settings.
   • Click Build Siril Script
   • The application writes its .ssf script file into the working directory

7. Run Siril Script

• Click the Run Siril Script button in the main window.
• The application automatically executes the configured run_project.ssf Siril script via the Siril Python API or uses the siril-cli as a backup
• Progress and script output appear in the console log panel in Siril and in a log file in the working directory
• When finished, your combined stack is saved automatically as [ProjectName]_final.fit and loaded into Siril

---

🕒 Typical Workflow Timeline

Step	Action	Time
①	Launch Siril & Python app	1 min
②	Create or Load project & verify sessions	2 min
②	Configure Settings and Images	5 min
③	Generate scripts	< 1 min
④	Run Siril script	Typicallly 5-??? minutes per session depending on the # of subs

---

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. See <https://www.gnu.org/licenses/>.