How to Add Stars in Photoshop

How to Add Stars in Photoshop

Night photography doesn’t always cooperate. Light pollution, clouds, or an exposure that wasn’t quite long enough can leave a night sky looking empty even when the rest of the shot is great. Compositing in a separate star photograph is a quick way to fix that, and the whole process comes down to one blend mode and a layer mask.

Bringing Your Star Photo Into the Background Image

Start with two images: your background photo and a separate star photograph, either one you’ve shot yourself or a stock image of a starry sky. With the Move tool selected, click and drag the star photo directly onto the background image so both live in the same document as separate layers.

Sizing and Positioning the Star Layer

The star photo usually won’t be large enough to cover the entire frame right away. Press Ctrl or Cmd+T to bring up Free Transform and stretch the star layer out until it covers the horizon. Be careful not to scale it up too far, though — stars that get stretched too large stop looking like real stars and start looking obviously fake, since actual stars in the night sky are quite small and evenly distributed.

Switching to Screen Blend Mode

Once the star layer is roughly positioned, change its blend mode from Normal to Screen. Screen blend mode makes black pixels completely invisible and only shows the lighter pixels, which means the black sky around each star disappears and only the stars themselves show through onto the background. This single change is what makes the whole composite possible — without it, the star layer would just sit as an opaque rectangle covering everything underneath.

Filling Gaps by Duplicating the Star Layer

Stretching a single star photo to fit the frame often leaves empty gaps on the left and right sides where the original image simply didn’t have any content. Duplicate the star layer with Ctrl or Cmd+J, then drag the duplicate over to fill one of the gaps, using the arrow keys to nudge it into perfect alignment. Repeat the process for the other side. If a recognizable feature like the Milky Way ends up repeating in an obvious way, Free Transform can scale or rotate that duplicate slightly so the repetition isn’t as noticeable — since these are just stars rather than a recognizable subject like a face, flipping or rotating a duplicate doesn’t read as a mistake the way it would on a person.

Merging the Duplicated Star Layers

Once all the duplicates are positioned to fill the frame, select all of the star layers together and merge them with Ctrl or Cmd+E. This combines everything into a single layer, which is easier to manage going forward. One thing to watch for: merging layers resets the blend mode to Normal, so remember to switch the merged layer’s blend mode back to Screen afterward.

Using a Clipped Levels Adjustment to Blend the Stars

Even with the Screen blend mode doing its job, the merged star layer often still carries too much light information, making the sky look overly bright or busy rather than like a natural star field. A Levels adjustment layer fixes this. Go to Layer, down to New Adjustment Layer, and over to Levels, then right-click the new adjustment layer and choose Create Clipping Mask so it only affects the star layer beneath it rather than the whole image. Because the star layer is in Screen mode, dragging the middle (midtone) slider to the right darkens the star layer, and its darker parts simply disappear, leaving just the brightest points — the actual stars — visible. Find a middle ground rather than pushing it to an extreme; the goal is for the stars to look like they’re part of the original sky rather than an obviously separate layer sitting on top.

Masking the Stars to the Sky

At this point the stars will likely be overlapping parts of the image where they don’t belong, like mountains, a house, or trees along the horizon. Group the star layer together with its Levels adjustment layer by shift-clicking both and pressing Ctrl or Cmd+G, then add a layer mask to the group so the stars only appear in the sky.

Selecting the Horizon with the Magic Wand Tool

Hide the group temporarily and create a new layer to work on. Press W for the Magic Wand tool and click in the sky, holding Shift and clicking a couple more times to include all of the sky until you have a clean line following the horizon — the exact shape of the terrain along the top edge, like where it meets trees, a house, or mountains. The area above that line doesn’t need to be perfectly selected yet, since it can be filled in separately.

Filling In the Layer Mask with White

With the horizon selection made, turn the group back on and click the layer mask button. Whenever a selection is active, that button loads the selection into the new mask. Anything not yet covered above the horizon line can be selected with the Lasso tool and filled with white using Edit, then Fill — white on a layer mask makes an area visible, black makes it invisible, so the sky above the horizon needs to be white and the ground below needs to be black. Hold Alt or Option while clicking the mask thumbnail to view the mask directly and check that the shape is clean. Once the mask is filled in, the stars will only be visible in the sky and hidden behind the mountains, trees, and any other foreground elements.

With the stars properly masked, you can still reposition them for the best composition. Free Transform still works on the grouped layers, letting you move, scale, or rotate the star field until it sits exactly where you want it, and a soft black brush painted directly on the mask near the horizon can fade the stars out gradually as they approach the ground for an even more natural transition.

Why This Technique Works

The whole effect rests on the Screen blend mode’s core behavior: black disappears, light shows through. That single property means a star photo can be layered onto any background without ever needing to manually erase the black sky around each star. Clipping a Levels adjustment to the star layer, rather than adjusting levels globally, keeps the change isolated to just the stars, letting you push the contrast until only the brightest points remain visible without affecting the underlying photo at all. And building the layer mask from the actual horizon line, using the Magic Wand tool to trace it, ensures the stars stay exactly where they belong — in the sky, and nowhere else.

Final Thoughts

Adding stars to a night photo takes only a few steps once you understand the underlying blend mode trick: bring in a star photo, switch it to Screen, fill any gaps with duplicated and repositioned copies, clip a Levels adjustment to control the brightness, and mask the result to the sky using the horizon as your guide. It’s a fast fix for a night sky that didn’t quite deliver on location, and it can make a real difference in the final image.

Quick Reference: Keys, Menus and Settings

• Bring in the starsMove Tool, drag the star photo onto the background; F for full screen
• Scale a littleCmd/Ctrl + T, just enough to cover the horizon
• Hide the blackLayers panel blend mode: Screen
• Fill the gapsCmd/Ctrl + J, arrow keys to align; Cmd/Ctrl + E to merge, then Screen again
• Blend with LevelsLayer > New Adjustment Layer > Levels, right-click > Create Clipping Mask, middle slider to the right
• Mask to the skyCmd/Ctrl + G, W and Shift-click the sky, layer mask button, Edit > Fill with white
• Check the maskAlt/Option-click the mask thumbnail

No AI, no generative credits.