Creating Galaxies Using Photoshop

1. Create a new document in Photoshop (CTRL+N). I used Width: 1024, Height: 768.
   
2. 
   
3. Fill the background layer with black. (D, then ALT+Backspace).
   
4. 
   
5. Click on the Channels tab, and create a new Alpha channel by clicking the 'Create new channel' icon near the bottom of the panel (If the Channels tab isn't visible, check Windows > Channel on the file menu).
   
6. 
   
7. On the new 'Alpha 1' channel, add some noise by applying Filter > Noise > Add Noise.. Set Amount to 50%, Distribution to Uniform. Click OK.
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9. Apply Filter > Blur > Blur More.
   
10. 
    
11. Open the Levels dialog (CTRL+L) and use these three Input Levels: 61, 1.00, 84. Click OK.
    
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13. Hold CTRL and click the 'Alpha 1' thumbnail on the Channels panel to load the selection.
    
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15. Switch back to the Layers tab and create a new layer.
    
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17. Restore default colors by pressing D. Select the 'Pastel Yellow' color on the Swatches panel. Or if you want to set it manually, the hex number is fff799.
    
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19. Apply Filter > Render > Clouds.
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21. Create a new layer, and make sure you didn't deselect. If you did, load the selection again from the Alpha 1 channel.
    
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23. Expand the selection by 2 pixels (Select > Modify > Expand..).
    
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25. Fill the selection with white (D, X, then ALT+Backspace) and deselect (CTRL+D).
    
26. 
    
27. Apply Filter > Blur > Gaussian Blur.. with a radius of 2 pixels.
    
28. 
    
29. Change the opacity of the layer to ~40% (the option for this is directly under the label for the Layers tab).
    
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The large stars of the image should now be complete.
Part Two
On to the smaller stars:

1. Duplicate the 'Alpha 1' channel.
   
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3. Apply Filter > Distory > Glass.. Set Distortion to 6, Smoothness to 1, Texture to Frosted, and Scaling to 100%. Click OK.
   
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5. Create a new alpha channel.
   
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7. Apply Filter > Render > Difference Clouds.. press CTRL+F to apply it again.
   
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9. Load the selection, and switch back to the channel created in Step 1.
   
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11. Press D, then X, then fill the selection 3 or 4 times with ALT+Backspace. Deselect.
    
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13. Load the selection, and switch to the Layers tab.
    
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15. Create a new layer under the first two star layers. Fill the selection with white.
    
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The star backdrop is now complete, and should look similar to the attatched image.

Part Three
The next step will be the creation of the nebula. Follow these steps:

1. Create a new alpha channel.
   
2. 
   
3. Apply Filter > Render > Difference Clouds. Press CTRL+F twice to apply it again twice.
   
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5. Select the Brush tool (B), and a soft brush with a diameter of 100.
   
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7. Fill in around the edges of the canvas with black to create the basic nebula shape (It might help to use a 50% opacity and make several passes instead of one pass with 100% opacity.. And feel free to take some artistic liberty with the brush, and add some more detail to the clouds). See the attatched images for an example of the basic nebula shape.
8. 
   
9. Using the Lasso tool (L), make a slightly deformed, oval-like selection on the channel. The size of the selection should be fairly large, probably 1/4 to 1/5 the size of the entire image.
   
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11. Feather the selection by 32 pixels (ALT+CTRL+D). Click OK.
    
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13. Apply Filter > Distort > Spherize.. Set the Amount to 100%, click OK.
    
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15. Repeat steps 5-7 several more times using different selections. Also, alternate between using 100% and -100% for the Spherize filter.
    
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17. Once again, using the Lasso tool (L), make a slightly deformed, oval-like selection on the channel. The size of the selection should be roughly the same as the selections made in Step 5.
    
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19. Apply Filter > Distort > Twirl.. Use the slider to make a nice twirl effect. I find the lower angle twirls look better than the smooth, spiral-like twirls of the higher angles.
    
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21. Repeat steps 9-10 several more times using different selections.
    
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23. Select the Clone Stamp Tool (S). Open the Brushes panel (F5) and select a soft brush with a diameter of 100.
    
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25. In the Brushes panel, check Scattering and then select the 'Shape Dynamics' label. Set Size Jitter to 100%.
    
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27. Hold ALT and click to select a point on the image to use as a source for the Clone Stamp tool. Somewhere in the center will work best.
    
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29. Make very subtle, short clicks on different areas of the image for added detail. After using the size 100 brush, right click and lower the diameter and do it again. Do this until you achieve the desired effect. For an example of the shape so far, check the attatched images.
    
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31. Apply Filter > Sharpen > Sharpen. Press CTRL+F to apply it again.
    
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33. Duplicate the current channel.
    
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35. Open the Levels dialog and use these values: 76, 1.00, 255. Click OK.
    
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37. Adjust the Brightness to +100 (Image > Adjustments > Brightness/Contrast).
    
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39. Inverse the channel's color (CTRL+I).
    
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41. Load the selection, and return to the channel created in Step 1.
    
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43. Apply Filter > Brush Strokes > Accented Edges.. Set the Edge Width to 1, Brightness to 17, and Smoothness to 15. Click OK.
    
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45. Adjust the Brightness to +40. Click OK.
    
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47. Load the selection, and create a new layer above all the star layers.
    
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49. Fill the selection with a dark red. Deselect.
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51. Go back to the alpha channel and open the Levels dialog, and use these values: 39, 1.00, 255.
    
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53. Load the selection, and create a new layer above the last layer.
    
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55. Fill the selection with Pure Magenta.
    
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57. Switch back to the Channels tab, and again duplicate the channel created in Step 1.
    
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59. Open the Levels dialog and use these values: 134, 1.00, 255.
    
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61. Load the selection and create a new layer above the layer created in step 23.
    
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63. Fill the selection with yellow.
    
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That's it, you should have a decent looking image resembling a nebula. If not, go back and play with some of the values I used for the different filters. The clouds filter will never generate the same clouds, so each nebula created will be different and may require slightly different values.