Last Christmas I purchased two Twilight animals for my children: a Twilight Turtle for my son and a Twilight Ladybug for my daughter. These little animals have a plush underside with a hard plastic shell. The shell has many little holes in it shaped like stars (one is shaped like a crescent moon) and there is a small light inside. When your child pushes a button, the light lights up and pours through the star and moon shaped holes, creating a constellation on the ceiling. Better yet, there are three light colors from which to choose (and it is easy for your child to toggle among them).
These two things were among the best gifts I've bought for my kids, because they love them so much. The amount of light each gives off is perfect. It lights up the room just enough to ease the minds of little ones as they drift off. Better yet, after 45 minutes the lights automatically turn off. They use 3 "AAA" batteries, but we use ours every night and the batteries will last for months.
Each Twilight animal comes with a map to the constellations present on either the ladybug's or turtle's shell (Cloud B also makes a Twilight Sheep), but I have never tried to use it. Reading other reviews I found that some people complained about the accuracy of the stars and the fact that the light has to be placed in the center of the room for it to evenly disperse stars on the ceiling. This was never a concern of mine, but it may be a consideration for you.
Twilight animals are soft enough to put in bed with your child. My little boy turns his on every evening and I will always have the vision of little blue stars hitting his face as we sing Twinkle Twinkle at bedtime. After having done this nearly every night for more than a year, I have to say this is an excellent toy.