I have started a personal Astronomy overlay (perhaps, it should be
named Amateur Astronomy overlay). If you like, you can import some of
its packages into science overlay.
Overlay is hosted at http://github.com/monoid/gentoo-astronomy/
Following packages are currently included:
* SkyChart (aka Cartes du Ciel), binary
* VirtualMoon, binary
* JSatTrak, Java, depends on some ebuilds from java-overlay; needs more work
* IridiumFlares, Java
(SkyChart and VirtualMoon are binary packages because 64-bit version I
compiled from sources fails to work under amd64).