In the movie industry, the term ‘day for night’ refers to shooting a scene in daylight and underexposing it. In addition, the cinematographer adds a blue filter to make the scene look like it was shot at night. You can do the same thing with still images in post-processing. I photographed Half Dome in Yosemite National Park in the late afternoon, and in Adobe Camera Raw I used the exposure slider to darken the picture. I then moved the temperature slider toward the blue end of the spectrum. Finally, I added the Milky Way behind the famous icon of California. The key to making successful composites is to eliminate the telltale line around the subject from the original background -- in this case, the sky. To do that in Photoshop, with the mountain selected, I use Select > modify > expand. In the dialog box that opens, I choose one or two pixels. This expands the selection outward into the mountain. Then, I feather the edge one pixel with Select > modify > feather. When the new background is pasted into the selection (Edit > paste special > paste into), the juncture between the two images is perfect. My exposure time for the Milky Way was 20 seconds at f/2.8 with 2000 ISO.