Herschel Catalog Builder
A free, offline desktop app for planning, imaging and logging all 400 objects on the Astronomical League's Herschel 400 list. A companion to the Messier, Caldwell and Sharpless builders.
Download free Browse all toolsThe Herschel list - known to observers as the Herschel 400 - is the Astronomical League's selection of 400 of the best deep-sky objects from William and Caroline Herschel's catalogues - galaxies, open and globular clusters, planetary nebulae and bright nebulae - picked as the natural next challenge after the Messier list.
The builder lays out all 400 objects in NGC order on a single 20 × 20 chart. Each empty square shows its NGC number, type and common name, so you can see at a glance what you've captured and what's left. Drag your photos onto the window and each one lands in the right square: name your files by NGC number (NGC 891.jpg), or use the Messier or Caldwell number for the handful of objects that have one (M33.jpg, C23.jpg).
Right-click a photo to adjust its framing, rest your mouse on it for a 300 × 300 preview, switch the twinkling star border on or off, and export the finished chart as PNG, JPG or TIFF. Everything stays on your computer, and it runs on Windows and on both Apple Silicon and Intel Macs.
Frequently asked questions
What's new in version 1.3?
Right-click a photo to adjust its framing (move and zoom the crop, or show the whole photo). File names can now use object names as well as numbers. 16-bit and 32-bit TIFFs from Siril, PixInsight and other stacking software work, and unstretched (linear) stacks are brightened automatically. There's also Undo for removed or replaced photos, a progress bar for big batches, a Missing list you can save as a checklist, and a short welcome guide the first time the app opens.
Is it really free?
Yes. No account, no subscription and no ads. Download it and start.
Does it need the internet?
No. It runs entirely on your computer. Your photos, chart and logs never leave it - the app works from copies and never changes your original files.
Windows says "Windows protected your PC" - is it safe?
That warning appears for any app that isn't from the Microsoft Store. Click More info, then Run anyway. Some antivirus programs flag apps packaged this way by mistake; if yours removes it, restore it from its quarantine and allow it.
My Mac says it "cannot verify" the app.
The app isn't from the App Store, so macOS asks once. Click Done, open System Settings → Privacy & Security, scroll down and click Open Anyway. Pick the Apple Silicon download for M1-M4 Macs and the Intel download for older Macs.
What can I log for each object?
Right-click a photo and choose Add log / notes: dates, total exposure, sub length and count, gain or ISO, telescope or lens, camera, mount, filters, other equipment and your own notes. Each log is saved as a text file next to the photo, and a summary shows when you hover over it.
Why are a few Messier objects on the list?
The Herschel list is built from the Herschels' own catalogue, which re-observed a few objects Messier had already listed - such as NGC 598 (M33) and NGC 6514 (M20). The Astronomical League kept them, so the builder does too, and you can drop in a file named M33.jpg and it goes to NGC 598.
How do photos get matched to squares?
Name the file with its NGC number - NGC 891.jpg, ngc7814.tif - and it goes straight to the right square. Messier and Caldwell numbers work for list objects that have one. Anything else, drop it on the square you want.
Ready to start logging sessions?
Free, offline, and your data stays on your computer.
Version 1.3 · Updated November 2026