Heh, here's a little tutorial for quick and cool starscape.
On a new blank canvas start by choosing a dark blue colour - #18323a - and black and then go to Filter > Render > Clouds.
Then create a new layer, fill it with black and go to Filter > Noise > Add Noise and use values roughly as shown below.
Now you must adjust it, so go to Image > Adjustment > Levels and bring those sliders together until you see most of the 'stars' vanish as shown.
Now set the stars layer's blending mode to Screen so that the black vanishes and just the stars remain. Then add a Layer Mask to the layer and with a large fat brush just mask out blobs so that it seems a little less even.