The night ambience in SH5 is very realistic I would say
Scopes are useless at night when I hear the comments of most real skippers, the exception is the full moon being in the right direction, this would allow you to spot a 'silhouette' of a ship without using any zoom, the zoomed optics would not capture enough light to make anything visible. In SH5 this can work, but not in real-life. If you see the ship then it's enough already to mark a bearing on the map. Do it multiple times and have its approximate course and speed.
If a ship is really close at night, first make sure you are not colliding with it. Then just point-and-shoot if you are about 500m, so your torpedos will activate in time. Lead the target in its travel direction a bit, you need experience to hit.
The Deck Gun? Yes you can try it to slow the ship down, but then it will change its course and you have no chance to hit it with your torpedos anymore. Also where are the next patrols? They can materialize in no time, especially if you are on the English East coast, you don't have much time to fool around maybe.
Other than this: If the ship is further away but still visible you must combine more bearings with a fast plotting solution to get your sub in a decent firing position, and maybe it's better to leave your position so you remain out of sight and go for a better intercept position later.
Other possibility: the 4-bearing method if the ship goes out of sight, your sonar man can follow most targets even if not visible to you or your crew.
Happy hunting!
