The Digital Photography Book, Part 1 | Moon Tutorial – Book Extra
Including the Moon and Keeping Detail
The first step is to open both photos in Adobe Photoshop (a shot of the moon on an evening sky with no clouds around or behind it, and the photo you want the moon to appear in). Note: If your photos are in tabs, go under the Window menu, under Arrange, and choose Float All in Windows.
From the Toolbox, choose the Move tool (V). Then, click on the moon photo and drag-and-drop it right onto the other photo (in this case, it’s a nighttime shot of a barn).
Go to the Layers panel and change the moon layer’s blend mode from Normal to Lighten (as shown here). Doing this, on a background like this dark blue sky, hides the black square around the moon from view, leaving just the moon itself visible. The key is to make sure you place the moon over a photo with a dark sky (at least as dark as the blue one shown here, or darker).
The final step is to resize and position the moon where you want it in your photo. To resize the moon layer, press Command-T (PC: Ctrl-T) to bring up Free Transform. Press-and-hold the Shift key (to keep things proportional) and then grab any corner handle and click-and-drag inward to decrease the size of your moon. To reposition it, just move your cursor inside the Free Transform box and then click-and-drag it where you want it. When the size and position look good to you, just press the Return (PC: Enter) key to lock in your changes.