Use the Rectangular Marquee Tool to create a long and fairly thin rectangle. Fill the selection with white and rotate it as shown below. Deselect everything (Ctrl + D) and apply a 2px Gaussian Blur (Filter > Blur > Gaussian Blur).
Change the blending mode of the white rectangle layer to Soft Light and lower the opacity to 11%. Duplicate this layer a couple of times (Ctrl + J) and move each duplicate in a slightly different position to the right or to the left.
Create a new layer and choose the standard round soft brush. Lower the size to 2px and opacity to 30%. Paint some white outlines in the places indicated below. Double click the layer and add an outer glow effect.
Create a new layer and change the blending mode to Overlay. With the standard round soft brush at 30% opacity an 400px size click once or twice in the middle of the scene. By doing this we will put the focus on the middle of the scene.
Choose again the round soft brush and set the color to a muddy yellow (#a7b01d). Create a new layer and change the blending mode to Overlay. Paint over the areas indicated below with 20% opacity to add some color variation to our scene.
Open the file “Nebula”. Select all and copy paste in our scene. Change the blending mode to Color Dodge and lower the opacity to 60%. Use a layer mask to hide the middle portion.
Use one of the imported moon brushes to create a white moon near the tree. Change the blending mode to Color Dodge.
Create a Curves Adjustment Layer and use the settings shown below. This will increase the overall contrast and darken the scene.
Create a Brightness/Contrast Adjustment Layer and increase the contrast slider to 24.
Create a new layer from all the visible layers (Ctrl + Shift + Alt + E) and apply a sharpen effect (Filter > Sharpen > Unsharp Mask).
Create again a new layer from all the visible layers but this time apply a 15px Gaussian Blur. Change the blending mode to Soft Light and lower the opacity to 53%. Add a layer mask and hide the bottom part of the effect.
As you can see bluring and changing the blending mode to Soft Light or Overlay creates a very mellow glow effect that it is perfect for this celestial scene.