Firmament · Observing
Interactive companions to the Firmament Observer Series
Companion to The Lunar Observer's Guide
An engraved, interactive Moon. Set any date and the terminator moves with it, so you can see exactly which craters, rilles and mountain ranges will be throwing their longest shadows tonight.
Companion to The Southern Sky Observer's Guide
The whole southern sky from wherever you stand, drawn as an engraved plate. Set your location, date and time, and it shows you what is actually above your horizon — Milky Way, Magellanic Clouds and all.
Each atlas is a single self-contained file. There is no account, nothing to install, and no connection required once you have it. Under a dark sky you will usually have no signal at all — so download the file before you go out, and it will open straight from your laptop or tablet.