Contrast Curve Generator

A robust contrast curve analysis tool for astronomical imaging, featuring intelligent annotation placement and comprehensive statistical analysis.

Features

• Automatic star detection and centering
• Robust FITS header handling - handles corrupted or incomplete headers
• Detection limit calculation using median-absolute deviation (MAD) statistics
• Smart annotation placement that automatically avoids data points
• GUI interface for easy parameter adjustment
• Multiple filter presets (Sloan g', r', i', z')
• Configurable smoothing for contrast curves
• Comprehensive output including:
  • PSF FWHM measurements
  • λ/D calculations
  • Dynamic range analysis
  • High-quality plots with dual axis (arcsec and pixels)

Installation

Option 1: Windows Executable (Easiest)

1. Download ccurve.exe from this repository
2. Double-click to run - no installation required!

Option 2: Run from Source

1. Clone this repository
2. Create a virtual environment:

   python -m venv venv

3. Activate the virtual environment:
   • Windows: venv\Scripts\activate
   • Linux/Mac: source venv/bin/activate
4. Install dependencies:

   pip install -r requirements.txt

5. Run the application:

   python main.py

Usage

GUI Mode (Default)

Simply run the executable or python main.py without arguments to launch the GUI:

1. Browse to select your FITS file
2. Load the file to read header information
3. Adjust parameters as needed:
   • Target name
   • Telescope specifications
   • Pixel scale and wavelength
   • Analysis radius range
   • Smoothing level
4. Click Generate Contrast Curve to create the plot

Command Line Mode

You can also run the tool from the command line:

python main.py your_image.fits

The tool will automatically:

• Extract metadata from the FITS header
• Calculate the contrast curve
• Display the plot

Parameters

• Target Name: Name of the observed object
• Telescope Name: Name of the telescope used
• Diameter: Telescope diameter in inches
• Confidence Level (σ): Detection threshold (default: 5σ)
• Min/Max Radius: Analysis range in pixels
• Pixel Scale: Image scale in arcseconds per pixel
• Wavelength: Observation wavelength in nanometers
• Smoothing (sigma): Gaussian smoothing level (0=none, 5=aggressive)

Method

The tool implements a robust statistical method for contrast curve generation:

1. Extrema Detection: Identifies all local maxima and minima in concentric annuli around the star
2. Statistical Analysis:
   • Calculates median values to resist outliers
   • Uses MAD (Median Absolute Deviation) for robust standard deviation estimation
3. Detection Limit:

   Detection Limit = median(maxima) + 5 × avg(σ_maxima, σ_minima)
   

4. Smart Visualization: Automatically places annotations to avoid obscuring data points

Output

The generated plots include:

• Scatter plot of local maxima (empty squares) and minima (dots)
• 5σ detection limit curve (red line)
• Dual x-axis showing separation in both arcseconds and pixels
• Information box with:
  • Target and telescope details
  • Pixel scale and PSF FWHM
  • λ/D and dynamic range
  • Observation date (if available)
• Automatic detection annotation for significant detections

License

This tool is provided as-is for astronomical research purposes.

Author

Generated with assistance from Claude Code