Open a new Photoshop file with 1000 x 1500px.
“Star environment “
Set the foreground color to white and the background color to black. Create a new layer and colored this black. Use Filter / Noise / Add Noise with amount = 70% ( Distribution = Uniform; Monochromatic = on). Apply Image / Adjust / Brightness and Contrast with Brightness = -70 and Contrast = -10. After then go to Filter / Blur / Gaussian Blur with radius = 2. And finally we apply Levels (ctrl + l). Important are the left and middle sliders. Move they together until that the stars appear (see the settings on the Image aside).
It looks empty. To create more stars we have to reply the operation. That mean: create again a new layer – colored it black but set this time the layer blend mode to “Lighten”. Then apply Add Noise, Brightness and Contrast , Gaussian Blur and Levels again. Try to change a little bit the settings to create different star formations. You can also set the opacity down or delete with the Eraser some stars. The aim is, don’t create an equal star background.
Repeat this steps until you have enough stars.