ok first find the astronomy thingy executable - I suppose you know the name of the package and it is an rpm, then run
rpm -qs thenameofthepackage
find the location of excutable, right click on the desktop choose new=>link to application, fill in the blanks, and you got yourself an icon on the desktop linked to the application, now if you want to put it in the K menu open up an Xterm
[shell_prompt]# cd .kde/share/applink
you should see files with .desktop exention, see what's inside these files and create a new file application_name.desktop with contents similar to all the .desktop files just put the name of executable relevant to the application.
I hope it's clear.