🔭 The Problem

The Flexible Image Transport System (FITS) is the undisputed data standard in astronomy and astrophotography. Every FITS file starts with a standardized header containing essential metadata: optics focal length, sensor pixel sizes, camera gain, filters, exposure times, observation timestamps, and celestial coordinates (WCS).

In real-world astrophotography pipelines, metadata glitches are notoriously common:

• Plate Solving Failures: ASTAP, PlateSolve2, or N.I.N.A fail blind solving because focal length (FOCALLEN) or pixel dimensions (PIXSIZE1/XPIXSZ) were omitted by capture software.
• Stacking & Calibration Errors: Calibration software (Siril, DeepSkyStacker, Astro Pixel Processor) rejects dark/flat frames or groups lights incorrectly due to mismatched FILTER, EXPTIME, or GAIN.
• Corrupted Bayer Patterns: OSC images turn green or red upon debayering because the BAYERPAT tag (e.g., RGGB) is missing or formatted incorrectly.
• Data Archiving & Sharing: Standardizing OBJECT names, observer credits, and custom notes before submitting data to public observatories or AstroBin.

Fixing a single keyword previously required launching heavy desktop suites (PixInsight, SAOImage DS9, AstroImageJ) or writing Python scripts with astropy.io.fits.

The Solution: FITS Header Editor Online

To make this workflow effortless across any computer, tablet, or smartphone without installing dependencies, I created FITS Header Editor Online.

🔗 Live Link: https://abctool.info/fits-header-editor-online/

⚡ Core Features & Capabilities

1. 100% In-Browser Privacy & Speed

   • Files are parsed directly in your browser's local memory using modern JavaScript binary buffer manipulation.
   • Zero file uploads: Scientific raw data remains strictly confidential and secure. Works instantly even with large raw captures.

2. Strict FITS Standard Compliance

   • Built to conform to IAU FITS standard specifications (80-character card images, padded 2880-byte logical records).
   • Structural keywords (SIMPLE, BITPIX, NAXIS, NAXISn, EXTEND) are protected against accidental modifications to prevent image data corruption.

3. Smart Visual Interface

   • Live Search: Instant real-time filtering across keywords, values, and comments.
   • Category Breakdown: Automatically groups cards into Target, Camera/Optics, WCS (Astrometry), Date/Time, and Instrument tabs.
   • Type Safety: Seamlessly switch between String, Number, Boolean (T/F), and Comment card types.

4. Astronomical Quick Helpers

   • One-click helper buttons to quickly insert or modify essential parameters: + OBJECT, + EXPTIME, + FILTER, + BAYERPAT, + GAIN, + FOCALLEN, + PIXSIZE1, + OBSERVER.

5. Multi-Format Export Options

   • Save & Download FITS: Rebuilds the header and joins it with the original raw data block for full pipeline compatibility.
   • Export JSON: For script automation, developers, and web integrations.
   • Export TXT: For easy reading, archiving, and logging.

🛠️ How to Use

1. Visit https://abctool.info/fits-header-editor-online/
2. Drag & drop your .fits, .fit, or .fts file into the upload area (or click Load Sample FITS for a demo).
3. Search, filter, or use the Quick Helpers to edit keywords in place.
4. Click Save & Download FITS to get your repaired astronomical image.

I would love to hear your thoughts, feature suggestions, or edge cases. Feel free to try it out!