====== Image processing for astrophotography ======

The data and the Siril script can be found in this google drive folder: https://drive.google.com/drive/folders/1vW2kqUQbHBEYf9KfGACMadruxLblsAUO

===== Processing and Stacking Monochrome Astronomical Images in Siril =====

==== 1. Downloading and Installing Siril ====
  * Go to: https://siril.org/download/
  * Download the installer for your operating system.
  * Install:
    * Windows → run the .exe  
    * macOS → open .dmg and move Siril to Applications  
    * Linux → use AppImage or package manager

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==== 2. Setting Up StarNet++ and Script ====
=== 2.1 Download StarNet++ ===
  * Download StarNet++ from the provided link.
  * Extract the folder to a known location (example: C:/Siril/Starnet2/).

=== 2.2 Install the Siril Script (.ssf) ===
  * Download the provided script.
  * Place it in your Siril scripts directory:
    * Windows → C:\Users\<user>\AppData\Local\Siril\scripts\
    * macOS → ~/Library/Application Support/siril/scripts/
    * Linux → ~/.config/siril/scripts/

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==== 3. Downloading the Data ====
  * Download the dataset from the provided Drive link.
  * Extract everything into a working directory.

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==== 4. Sorting the Data into Filter Folders ====
The data is already calibrated. Only light frames are provided.

Create the following folders:

  * **L/**
  * **R/**
  * **G/**
  * **B/**
  * **HA/**

Move each filter’s images into its respective folder.

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==== 5. Opening the Project in Siril ====
  * Open Siril.
  * Click the **Home (house) icon** → top-left corner.
  * Navigate to the parent directory that contains the subfolders: L, R, G, B, HA.
  * Select that directory.

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==== 6. Running the Preprocessing Script ====
  * Go to **Scripts** tab.
  * Select the installed script.
  * Siril begins checking and preparing images.
  * Preview window appears.

To change preview mode:
  * Bottom bar → switch **Linear** ⇄ **AutoStretch**.

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==== 7. Background Extraction ====
  * Go to **Process → Background Extraction**.
  * Place sample points on dark, empty background areas.
  * Ensure no stars, nebula, or bright zones under the points.
  * Click **Apply** (Extract Background).

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==== 8. Plate Solving (Astrometry) ====
  * Go to **Analysis → Astrometry → Plate Solver**.
  * Enter:
    * Focal length  
    * Pixel size  
    * Camera sensor information  
  * These values are visible under **Image Information**.
  * Click **Solve**.

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==== 9. Color Calibration ====
=== 9.1 Photometric Color Calibration (SPCC) ===
  * Go to **Color → Photometric Color Calibration**.
  * If Gaia server is down → download Gaia catalog locally from Siril’s database manager.
  * Run SPCC.


==== 10. Stretching the Image ====
Stretch *before* star removal for best results.

  * Go to **Image Processing → Histogram Transformation**.
  * Use **AutoStretch** or adjust:
    * Black point  
    * Mid-level  
    * White point  
  * Apply the stretch.

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==== 11. Star Removal with StarNet++ ====
  * Go to **Process → Star Removal → StarNet++**.
  * Set the StarNet++ executable path if prompted.
  * Enable:
    * “Create starless image”
    * “Create star mask”
  * Run StarNet++.

Output:
  * One starless image
  * One stars-only image

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==== 12. Post-Processing ====
=== 12.1 Color Saturation ===
  * Go to **Color → Saturation**.
  * Increase moderately.

=== 12.2 Curves ===
  * Go to **Image Processing → Curves**.
  * Adjust luminance/RGB to preference.

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==== 13. Re-Adding Stars ====
  * Go to **Image Processing → Star Processing → star recomposition**.
  * Combine:
    ``starless + stars``
  * Apply to produce the final image.

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==== 14. Saving the Final Image ====
  * Go to **File → Save As**.
  * Export as TIFF, PNG, or FITS.