Sights on some Bf 110s?

[Threedp]

I can't see through the sights on some of the ETO Bf 110s in non-night scenarios, particularly the nightfighter versions. Are they specialized sights? Do I have to do something to 'turn them on' as I'm not seeing much advantage over normal sights at night?

 

[HouseHobbit]

Hit "L" and this turns on the lights for the cockpit..