I have the Canon 28mm f1.8 that I used with my mkII, it's a great lens and quite good for nightscapes, examples
here.
I'm actually going to sell it now that I don't have the mkII anymore, just FYI
Also the 40mm STM pancake lens is awesome for the price and, apart from being an excellent walk around lens, it produced surprisingly good results when shooting the night sky - basically edge to edge sharp stars wide open at f2.8.