Convert JJ to FITS

Need to convert hundreds of JJ files to FITS? reaConverter does it in one click. No file limits, no watermarks, no internet required.

Tired of converting JJ files one at a time? reaConverter processes entire folders to FITS automatically. Handles large batches reliably without crashes or timeouts.

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JJ to FITS
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How to Convert Multiple JJ Files to FITS?

1. Download and Install reaConverter

First, grab reaConverter from the download button below. Installation is fast, and the software runs offline — no account or signup needed.

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Install reaConverter

2. Load your JJ files

Add JJ files to reaConverter. One file or a thousand, the process is the same. Everything runs locally on your machine.

You can drag-and-drop files, browse to a folder, or add entire directory trees including subfolders.

Load your JJ files into reaConverter

3. Select FITS as output format

Select FITS from the output format list and set your destination folder. You can also adjust quality and compression settings.

Select FITS as output format

4. Start JJ to FITS conversion

Click the Convert button to start. reaConverter will process all your files with the settings you selected.

Start Conversion

When finished, your new .fits files will be waiting in the destination folder.

JJ to FITS Converter

reaConverter offers the fastest, simplest solution for converting your JJ files into FITS in seconds - all files processed on your PC for maximum privacy and speed.

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Do more with your files

Converting JJ files for use in a workflow? reaConverter offers many ways to process files, so you can customize them according to your requirements.

Our range of editing options includes auto-processing options such as auto-rotate, auto-crop, watermarking and more. Change Color Space, copy Metadata, set DPI, manage ICC Profile, control Bit Depth.

Conversion features
Image editing

User Reviews

Average User Rating:
Last updated on January 25, 2026
"reaConverter makes FITS conversion incredibly easy. We batch convert astronomical images to standard formats for presentations and analysis, all automated through the command-line. It’s fast, reliable, and handles large datasets without issues."
Laura N.
Laura N.
Astrophysics Research Assistant
"Essential for our astroimaging pipeline! reaConverter perfectly handles FITS files from our research telescope, preserving all WCS coordinates and photometric data during batch conversion to TIFF. Now we process 100+ deep-sky exposures nightly without losing critical metadata for our exoplanet studies!"
Joseph Wilson
Joseph Wilson
Satisfied Customer
"An excellent program! I use it regularly in my work - it supports nearly every file format imaginable. The interface is intuitive and runs flawlessly every time."
Roger Cook
Roger Cook
Happy User
"For agencies handling confidential data, reaConverter eliminates cloud-upload risks while delivering unmatched conversion reliability. Our team uses it both in-office and remotely with identical results."
Jamal Bailey
Jamal Bailey
Satisfied Customer
"Our volunteer team uses reaConverter to prepare images for fundraising campaigns. The learning curve was minimal, and the results are professional-grade. The customer support team even helped us customize a workflow — fantastic service!"
Jason P. Bailey
Jason P. Bailey
Non-Profit Coordinator
"An efficient all-in-one solution for image conversion and light editing, designed for maximum user-friendliness."
Elena Anderson
Elena Anderson
Happy User

JJ to FITS Conversion: FAQ

What are JJ files?

JJ is a compressed image format associated with Doodle, a graphics editing software program that used to work on Commodore 64 computers. This was one of the first brands of home computers to gain wide popularity and it was sold extensively during the 1980s. At the current moment, JJ is considered an obsolete and rare format.

What are FITS files?

The FITS (Flexible Image Transport System) format is a standard format used particularly for storing, transferring and processing scientific images from fields such as astronomy. FITS was first launched as an open standard in the early 1980s and has gone through several subsequent upgrades. FITS files contain not just images, but also data related to photometry and spatial calibration, and information about the origin of the image. Similar formats include FIT and FTS.

Can reaConverter convert JJ to FITS?

Yes! reaConverter instantly converts .jj to .fits with perfect quality preservation. With its batch processing feature, you can convert multiple files at once in just a few clicks. You can even convert images directly from Windows Explorer using the right-click menu — fast and convenient.

Can I convert JJ to FITS online?

If you only need to convert a few JJ files to FITS format, feel free to try our free online free online JJ to FITS converter — perfect for small batches with no installation needed!

How can I turn JJ files into FITS on my computer?

The best way to change JJs to FITSs on your PC is to install a quality piece of software, such as reaConverter. This software is extremely efficient in managing a wide range of batch files conversions, including conversion from JJ to FITS.

How can I automate JJ to FITS files conversion?

reaConverter supports all the most useful automation features such as right-click сonversion and Watch Folders for the most efficient automated files conversion in any software of this type.

Is there a way to convert JJ files to FITS using the command prompt?

reaConverter provides full access to all its features via Windows command line, including a high-performance command-line jj to fits converter for batch processing.

What else can I do with reaConverter?

Set file dateConvert GIS filesConvert CAD formatsSet picture bit depthConvert Gerber images

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