vdB Catalog Builder
A free, offline desktop app for planning, imaging and logging all 158 of Sidney van den Bergh's reflection nebulae - the blue and golden dust clouds lit by nearby stars, from the Iris and the Witch Head to the Pleiades. A companion to the Messier, Caldwell and Sharpless builders.
Download free Browse all toolsReflection nebulae shine by starlight scattered off dust rather than by their own glow, which gives them their soft blue and golden colours. In 1966 the Canadian astronomer Sidney van den Bergh catalogued 158 of them from the Palomar Observatory Sky Survey plates - a concise, curated list of some of the most beautiful dust in the sky.
The builder lays out vdB 1 to vdB 158 on one chart, with well-known objects named on their squares - the Iris Nebula (vdB 139), the Witch Head (vdB 36), M78 (vdB 59) and the Pleiades nebulosity (vdB 20-23). Drag your photos onto the window and each one lands in the right square: name your files vdB 139.jpg or vdb142.png, or use another designation such as NGC 7023 or IC 2118.
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 reflection nebulae blue?
Dust scatters blue starlight more strongly than red - the same reason the daytime sky is blue - so most reflection nebulae look blue. Around cooler, yellower stars the light they reflect looks golden instead.
How do photos get matched to squares?
Name the file with its vdB number - vdB 139.jpg, vdb142.tif, van den Bergh 24.png - and it goes straight to the right square. Many other designations work too (NGC 7023, IC 2118, IC 4592, M78, Sh2-136...), as do names like Iris, Witch Head, Merope, Angel and Ghost. 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