Excellent pickup Leon, you're going to love the 50L.
I've got the 85L and absolutely adore it !
Here's a shot I did with it on
Rho Ophiuchus Neb Region.
The only thing to watch on these two lenses is that you have to get the focus critically spot on.
Even if you're only just very slightly off, you will get colour fringing around the stars, purple one way, orange/yellow the other way.
It really is critical on these two lenses more-so than other L lenses especially when using them close to wide open.