If the cover is open and rocky enough to make deep diving cranks a good bet, I like to throw them anytime that there is sun hitting the water. Shallow cranks can be brought through open water near cover and are also good during daylight hours, even if the light is barely hitting that part of the water. Of course, one of my best nights for numbers of bass was throwing a Mann's 1- painted black in a lake with lots of flooded brush along the edges, working it as slow as it would still kick, on a rising 1/4 moon like what we have right now.
Tight lines,
Wade