Vignetting in most f/5.6 LF lenses stops at f/11--this is true for my Rodenstock 55mm, 90mm, and 135mm. However, that is just mechanical vignetting. The wide lenses will have a certain amount of natural vignetting.
You will also have to take care that your film does not shift with humidity during exposure. Many LF astrophotographers convert a 4x5 film holder to a vacuum back. I have heard of folks putting a small piece of double sided tape in the center of the holder to hold the film--but that always seemed a pain to me for various reasons. You may want a cloth to cover the camera so to reduce dewing. There is also the possibility of the lens getting dew on it.
But good luck. More folks should take their cameras out at night--including me.