I use a digital minute timer/outlet that I picked up out of harbor freight for like 7 bucks about a year ago. I run it during the day only because I dont want temps to drop too low and I feel the spray disturbs them at night. What I have done in the past is run a warm humidifier on during the dry season just to keep humidity up. It depends on your cham type. Yemens and carpets are tougher. Jacksons not so much, so they need the extra tlc.
I really like the timer that came with my Mistking kit. It's digital, has eight different timers that you can set, and will let you set the timers down to the second. I tried a few digital timers from Wal-Mart and Home Depot but they weren't nearly as nice as far as adjustability and quality goes so now I use them to control the lighting lol.
The digital ones Ive got at walmart or radioshack or homedepot have always worked fine as well.
You dont want to mist at nite really. Its generally recommended to make sure your last misting of the day is early enough for everything to dry out before lights off. This way mold and mildew arent encouraged.