Bitcoin is way frequently traded with small time frames, because of price fluctuations which create good opportunity to earn funds on these roller-coasters. As for the night, then yeah, due to the low activity level on the market, price is deprived of high fluctuations, but at the same time it doesn't become more predictable.
You anyway need to run a thorough analysis, and I presume that the best time frame which suits this purpose - H1, you can also consider M30.