The problem you are having is the general lack of ambient lighting in Odyssey. While the settlement is in shadow, there should be plenty enough ambient light to make details of buildings, etc visible. Unfortunately, Odyssey only seems to do direct lighting so it's too dark.
Believe it or not, though, the lighting has been getting better. During the alpha, you could walk under an awning during the day and suddenly couldn't see anything (including the day lit parts of the settlement outside the awning) without a flashlight.