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Image processing for astrophotography

1. Stacking in DeepSkyStacker (DSS)

  1. Install DSS by downloading the installer appropriate for your OS from this page:

https://github.com/deepskystacker/DSS/releases/tag/6.1.0 (scroll to the bottom → “Assets”)

  1. Download some raw data from here: (add link)
  1. Open the DeepSkyStacker app

(⚠️ Not “Live DeepSkyStacker”)

  1. Click on Open picture files … on the top-left corner of the sidebar.

Select the downloaded FITS photos. These are your light frames.

  1. Click on Dark, Flat, and Offset/Bias buttons consecutively to add the calibration files.
  1. Make sure that all images in every tab are selected in the bottom panel.

If not, click on Check all in the second section of the left sidebar.

  1. Click on Register checked pictures…
  1. Uncheck Stack after registering

  1. Go to the Advanced tab → click Check the number of detected stars.

DSS will detect stars in the reference frame.

  1. If the number is less than 60, lower the detection threshold and click Detect stars again.

A good range is 60–300 stars.

  1. After confirming the star count is good, return to the main window.
  1. Click on Stack checked pictures.
  1. Choose the default stacking settings unless otherwise instructed, then click OK.
  1. DSS will begin stacking. When finished, it will open the stacked autosave image.
  1. Save the final stacked file as:
    • 32 bit FITS file

(recommended for further processing in Siril/PixInsight/Photoshop)


End of DSS Section

Processing and Stacking Monochrome Astronomical Images in Siril

1. Downloading and Installing Siril

  • 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

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/

3. Downloading the Data

  • Download the dataset from the provided Drive link.
  • Extract everything into a working directory.

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.


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.

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 LinearAutoStretch.

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).

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.

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.

9.2 LPCC (Local Photometric Calibration)

  • Go to Color → Linear Photometric Color Calibration.
  • Load local Gaia index file.
  • Run LPCC.

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.

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

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.

13. Re-Adding Stars

  • Go to Image Processing → Star Processing → star recomposition.
  • Combine:

``starless + stars``

  • Apply to produce the final image.

14. Saving the Final Image

  • Go to File → Save As.
  • Export as TIFF, PNG, or FITS.
courses/ast100/ip.1765347184.txt.gz · Last modified: by shahal

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