FREE Astronomy Software

List of useful astronomy software.
All free to download and use, at the time of writing.

Planetarium Software
Stellarium - Sky simulation - VERY good
Cartes du Ciel - Sky charts - Simpler and less resource-hungry than Stellarium, but more objects plotted.
Asynx Planetarium
Celestia
HN-Sky
Where is M13
StarCalc
C-Nebula-X
Sky Atlas

Dark Adaption - Turn your screen red to preserve your night-vision
Backyard Red
Dark Adapted

Image stacking
Registax 6
Rot and Stack
K3CCD tools - old free version
Deep Sky Stacker
Startrails - Create star trail images

Lunar Mapping
Virtual Moon Atlas
LunaView

Misc.
NEWT - Newtonian design software

...more to come