KStars is a Desktop Planetarium by KDE. It provides an accurate graphical simulation of the night sky, from any location on Earth, at any date and time. The display includes up to 100 million stars, 13,000 deep-sky objects, all 8 planets, the Sun and Moon, and thousands of comets and asteroids.
This is a very professional tool for not only amateur astronomers, but for professional astronomers. It’s trade-free, because it doesn’t ask for anything from the user.