The Messier Catalog Builder is a free desktop app for planning and logging your sessions across all 110 objects in the Messier catalog — the galaxies, clusters and nebulae that make up the backbone of any deep-sky imaging list. Nearly the whole list sits in the northern sky, so it's well within reach for astrophotographers across North America and Europe.
It lays out the full catalog as a single chart, one tile per object. Drag your own captures onto the grid — name a file like M42.jpg or M31.jpg and it drops into the right tile automatically — and watch your progress counter climb as you fill in the catalog.
For each object you can log your exposure time, sub-length and count, gain, and the equipment you used, along with your own notes. Over a season (or several), it builds into a complete record of what you've captured, what's left, and what settings worked well on a given target.
It's a native desktop application rather than a web page, so it runs offline on your own machine and your logs stay local — nothing is uploaded anywhere. Available for Windows and macOS (both Apple Silicon and Intel). It's also the direct companion to the Caldwell and Sharpless Catalog Builders below, so if you track all three lists you can use the same workflow across every target you image.
