Open your night shot up in Photoshop and create a new layer above it. Rename it 'Sky', make sure it's selected and go to Edit>Fill. In the Use box select Black and hit OK to paint your new layer black.
This has created a base for our stars to sit on. To create stars we need to add some noise to the image so go to Filter>Noise>Add Noise. Make sure Gaussian and Monochromatic are selected and change the percentage to around 90%. If you think more stars are needed just move the slider up then Click OK.
Next, you need to move the 'Sky' Layer under the layer that has your original shot in. This will hide the stars from view but this is easily rectified by clicking on the top layer and changing its blending mode from normal to screen. When applied, click back on the 'Sky' layer and then click the adjustment layer icon and select Levels.
We are doing this as there's far too many stars in the sky for it to be believable. When the new window opens, drag the right pointer more to the right to remove some of the stars. Our sky now looks better but stars are still sitting over parts of the image they shouldn't be so select the 'Sky' layer, pick up the Erase tool and brush over the parts of the image you don't want the stars to sit over. In our case it's ones that were sat at tree level or were a little too close to the houses in the background. You can also remove more of the stars from the sky if you wish to create a more irregular pattern. Your image now has its new, star-filled sky.
Click on the image to see the stars more clearly:
Note: If you go to save the image for web and encounter a problem with the adjustments vanishing try resizing the image (Image>Image Size) before you do the save for web action. The only variable will be how much you have to reduce the dimensions of the file by. There's a little trial and error involved but it does work eventually!
Create a stylish website with ease with foliopic – a template-based website builder for photographers and artists.