AstroImageJ – ImageJ for Astronomy

AstroImageJ (AIJ) is a simple and powerful tool for astronomical image analysis and precise photometry.

AIJ provides an astronomy specific image display environment and tools for astronomy specific image calibration and data reduction.

Although AIJ maintains the general purpose image processing capabilities of ImageJ, AIJ is streamlined for time-series differential photometry, light curve detrending and fitting, and light curve plotting, especially for applications requiring ultra-precise light curves (e.g., exoplanet transits). AIJ reads and writes standard Flexible Image Transport System (FITS) files, as well as other common image formats, provides FITS header viewing and editing, and is World Coordinate System aware, including an automated interface to the web portal for plate solving images.

AIJ offers research grade image calibration and analysis tools with a GUI driven approach, and easily installed cross-platform compatibility. It enables new users, even at the level of undergraduate student, high school student, or amateur astronomer, to quickly start processing, modeling, and plotting astronomical image data with one tightly integrated software package.

Features include:

  • Provides an interactive interface similar to ds9.
  • Reads and writes FITS images with standard headers.
  • Allows FITS header viewing and editing.
  • Plate solves and adds WCS to images seamlessly using the web interface.
  • Displays astronomical coordinates for images with WCS.
  • Provides object identification via an embedded SIMBAD interface.
  • Aligns image sequences using WCS headers or by using apertures to correlate stars.
  • Image calibration including bias, dark, flat, and non-linearity correction with option to run in real-time.
  • Interactive time-series differential photometry interface with option to run in real-time.
  • Allows comparison star ensemble changes without re-running differential photometry.
  • Provides an interactive multi-curve plotting tool streamlined for plotting light curves.
  • Includes an interactive light curve fitting interface with simultaneous detrending.
  • Allows non-destructive object annotations/labels using FITS header keywords.
  • Provides a time and coordinate converter tool with capability to update/enhance FITS header content (AIRMASS, BJD, etc.).
  • Exports analyses formatted as spreadsheets.
  • Creates color images and with native ImageJ processing power.
  • Optionally enter reference star apparent magnitudes to calculate target star magnitudes automatically.
  • Optionally create Minor Planet Center (MPC) format for direct submission of data to the MPC.
  • Nearby eclipsing binary star identification from expected depth versus light curve RMS table for TESS follow-up.
  • Delta-magnitude versus RMS plot.
  • Enhanced contrast controls.
  • Annotations are retained when placing apertures.
  • FITS header search feature.
  • Cross-platform support – runs under Linux, Mac OS X, Windows, and other operating systems that support Java.

Support: User Guide, Forum
Developer: Karen Collins, John Kielkpof – University of Louisville
License: GNU General Public License (GPLv3)


AstroImageJ is written in Java. Learn Java with our recommended free books and free tutorials.

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