And now for something completely different. It occurred to me that some of you might be interested in a guide to making stars like I did for the Diskworld post. It's actually not too complicated. And besides, if you want apple pie you've got to learn to make a universe.
This tutorial has lots of pictures, so I'm putting it behind a cut so as not to clog up anyone's RSS. It's SFW, I promise!
Step 1: Create Photoshop Document. Name it 'Stars'. Give yourself a nice big square field at a high resolution, 10x10 inches at 400 pixels per inch is what I'm using here.
Step 2: Fill with Black. Paintbucket tool for the uninitiated. Make this on a new layer, not the background.
Step 3: We need some basic speckles to work with. Go to Filter>Noise>Add Noise. Move the slider to between 10 and 20%. (Higher percentage will give you a more dense star field, a lower percentage will have more black space in it. I'm taking the middle path, 16.57%.) Make sure that Guassian and Monochromatic boxes are checked.
Step 4: Image>Adjustments>Threshold. Drag that sucker down to 98.
If you could see what you were doing before, you definitely won't be able to now. This would be a good time to zoom way in to reassure yourself that you're actually doing something. Ah yes, see? Progress.
Step 5: Add a new black layer below your active layer. Rename your active layer 'stars 1' to help keep things straight.
Step 6: Now, while you're all zoomed in and are working on your stars 1 layer, we'll use the magic wand tool. Adjust your settings magic wand settings so that the Contiguous box is not checked, and the tolerance should be set to 2. Then select all the black.
Aaaaand delete it.
With the black layer in place underneath, you've separated your black from your stars. This will become important in a minute.
Step 7: Select one quarter of your stars 1 layer using the rectangular select tool. It will be easiest to do this if you zoom out and can see the whole workable field.
Copy it and paste to a new layer, named stars 2.
Step 8: While on your new stars 2 layer, go under Edit>Transform>Scale, (hold down shift to keep the proportions the same) and scale your stars 2 layer way up, until it is covering the whole workable surface. Don't worry about overshooting a bit.
Step 9: Select one quarter of the stars 2 layer, copy it and scale the copy up in exactly the same way. Name the new layer stars 3.
Step 10: One last time, same deal: Select a quadrant of stars 3, copy onto new layer stars 4, and scale up until it covers the whole workable surface. You should have something that looks like this:
Now you should have four layers of stars in order from largest to smallest, with a black backdrop underneath them. If all you want is a simple background, you could stop here. Yay!
But you might want to stick around, as we're just getting to the fun part. And by fun I mean 'more likely to ruin everything forever'.
The next bit is much more freeform. We'll be using the eraser tool, the blur tool, gaussian blur, and copy and paste to make things look a little more chaotic and realistic.
Step 11: In order to sidestep that 'ruin everything forever' problem, duplicate your layers. Make a group (create a group by clicking the folder symbol at the bottom of the layer box) named Basic stars.
Select all the layers you've made, then Layer>Duplicate layer. Take the copies and drag them into Basic stars.
This is your backup in the event you'd like to start over.
If you now have one set of five layers in a group and one set of five layers *not* in the group, you're golden.
Step 12: Hide the contents of Basic starfield, and make it invisible. (click the eyeball symbol next to a layer or group to turn visibility on and off.)
Now that your backup's all done, let's get to work!
Step 13: We'll begin on the biggest nearest stars, the stars 4 layer. For the moment, make all other layers invisible. Set your eraser tool on 50% opacity and a nice big radius of 300. Now start shaping your stars. Remember that one or two swipes will make a star dim, but not invisible. I'm going to shape my stars into a sort of swoop, thinking to emulate the horsehead nebula. Remember to leave a few clear outliers which are not part of whatever formation you are shaping. This is my version of stars 4, with all the other layers invisible.
Step 14: Now, my other layers need to be shaped as well. One by one make them visible, and shape them down with the eraser tool. Don't be too exact about your edges! This next image is while I am working on my stars 3 layer. I have stars 4 visible as well to help show me where the edges of my formation are. Feel free to adjust the opacity of the eraser if you feel it's taking away too much, or not enough. If you feel like you've made a mistake and wish to try again, just copy the un-erased version of that layer from your Basic starfield group, drag it into place, and hide your first attempt.
Step 15: After some erasing, here's what my layers look like all together.
This would also be a totally reasonable place to stop, depending on how you want to use your picture. But it all seems a little sharp to me, so I'm going to add some stardust.
Step 16: Duplicate all your stars layers again. Then merge all the duplicates into one layer. (Both of these commands are under the layers menu) On your merged layer, select a section of starscape you think could use some cloudiness.
Step 17: Copy your selection to a new layer. Name this layer with the small selection pasted on it 'Cloud'. Turn off visibility on your merged layer.
Flip your Cloud layer vertically (or horizontally, as is appropriate to your picture) using edit>transform>flip horizontal.
Step 18: Name your new layer cloud, and run a fliter>blur>gaussian blur on it, with a radius of 5.
Step 19: That doesn't seem nearly cloudy enough to me, so I'm going to duplicate the layer, and rotate the copy so the stars are not directly overlapping. (I also shifted it down a bit.)
Now I'm going to merge my two cloud layers, and use the eraser tool (still with it's 50% opacity) to make the edges a little less obvious.
Step 20: Cleanup. If anything seems too bright to you, remember that you can tune down the brightness of an entire layer using the layer opacity in the layer box, and that if things seem too sharp you can use a smidge of gaussian blur on an entire layer. In this case I'm pretty pleased with everything, but I made the stars 1 layer invisible to increase contrast, did a little more selective shaping with my eraser on my stars 4 layer, and nixed a couple stars that were too close together or otherwise bothersome.
And I think I'm done.
But by all means, continue if you're having fun. Using these techniques you can make a very cloudy nebula, or enlarge a few outlier stars for effect, or make your own constellations. Go nuts! If you keep all your experimenting on separate layers, it's very easy to say 'eh, that didn't really work' and just revert to an earlier version.