In the original tutorial, Collis focuses on the Rule of Thirds, a method that simply states that if you divide your canvas in three lengthwise and vertically, your main focal points should be at the intersections, or along the lines themselves. The reason being for having your main focal point off center is that it creates a more visual interest. Take a look at this image from Collis:
Keeping that in mind, I'm going to keep my focal point in the bottom right corner.
Alright, let's start our composition. Create a new canvas. Mine will be rather large, at 1280x800. Use a radial gradient, with a rather subtle light color where the explosion will be. Make it somewhat like mine:
Now let's give it some texture. Create a new transparent layer. Go to Filters > Render > Clouds > Solid Noise. Use these settings:
Click ok. Set the cloudy layer's blending mode to Screen and lower the opacity to about 12%.
I chose to next use this stock due to it's texture (Right Click>Save As):
In your canvas window, go to File > Open As Layers. Open your aurora image. Rotate the image so the aurora runs lengthwise. You can also use the scale tool and adjust the aurora to better fit your image. Go to Colors > Desaturate and click Desaturate. Now get out a large, soft eraser and erase pretty much anything that isn't part of the aurora. You can leave the sky in it, though. Set the layer to Dodge and lower the opacity to 50%.
Now we are going to add the stars. Download this image of stars below:
Go to File > Open as Layers and select the star image. Lower the opacity to about 19-20%.
Now we'll add our planet. I am going to be using this planet found via Google:
Open up the planet as a new layer in our piece. Resize, rotate, and place it in the desired spot abiding by the Rule of Thirds I mentioned earlier.
Now let's give our planet a little more depth. Duplicate the planet layer. Run the dodge/burn tools over it. Make the top of the planet lighter, and the bottom of it darker. Set the layer mode to Screen.
Now let's add our planet into the image again. Do this by going to File > Open as Layers, and select your planet. Shrink the planet so it is even smaller, like in mine below. Desaturate it so it looks, well, different from our larger planet. Rotate it a bit, and use the dodge tool on the part where it will collide with the larger planet.
Get out the gradient tool, and select FG to Transparent. Make white your foreground color. Right click > Alpha to Selection on the planet layer. Create a new layer and apply the gradient to the selection, going from where the comet is, to the bottom of the planet. Select > Deselect. Set the layer mode to Overlay and lower the opacity a bit.
Go ahead and move the comet layer behind the planet layer. Create a new layer. Grab a large, soft brush and click only once or twice to get a nice, white, soft glow as shown.
Now use the scale tool and the rotate tool to elongate the light like I have done. Also be sure it is tangential to the main planet.
Now we'll add a blue glow to the outside of the light. Go to Filters > Light and Shadow > Drop Shadow. Make the X & Y Offsets 0, the radius 15, and do not allow resizing. Change the color to a darkish blue, or whatever matches your planet. Click ok.
Duplicate the glow layer and rotate it so it's opposite the last glow layer. Go to Filter > Repeat Drop Shadow. Your second glow should have the same glow as the first. Let's add some color to it now. Get out another large, soft brush. Now I want to stick with a sort of blue explosion. I'll make my brush blue. Paint the explosion a bit and set the layer mode to Overlay. Duplicate the layer. Set the new layer to Screen.
Duplicate one of the light layers. Go to Filters > Blur > Motion Blur. Use these settings:
Set the layer mode to Screen, and lower the opacity.
Now we want to create a tail behind our comet. Duplicate your layer we just made. Lower the opacity. Smush it a little and blur it a bit. Place it behind our comet. Give it some color if ya want. Remember to change opacities and such and to also play around a bit with what you're making. Makes it more, creative, I guess you could say.
Now we are going to grab this image found via Google:
We will use this image to form some of the tail lights on the comet. Open this image as a layer and place it behind our two planets. Use a soft eraser and erase everything except for what you see in the image below. It makes it look somewhat like particles are being thrown out by the collision. You can even duplicate the layers a couple times and make it different.
Right click on the planet layer and select Alpha to Selection. Create a new layer behind the planet layer named "backglow." Fill the selection with white. Select > Deselect. Press the Up & Left arrow keys a few times to move the white ellipse in the direction shown. Afterward, go to Filters > Blur > Gaussian Blur. Blur by 40. Click ok. Set the backglow layer to Overlay and duplicate it. Blur it again, and move it up and to the left even more.
Now we need the all-important lens flare. Create a new layer above all the others and fill it with black. Go to Filters > Light and Shadow > Lense Flare. Render your lense flare. Set the layer mode to Screen.
Now we'll apply a subtle blur to soften the whole image. Go to Edit > Copy Visible and Paste as Layer. You should now have a new layer with our WIP on it. Duplicate it. Hide one of them. Desaturate the visible one. Go to Filters > Blur > Motion Blur. Select Zoom as the type of blur. Play around with it until you get something like this:
Now set the blurred layer to Overlay at 20% opacity. Alright now grab the other layer we hid earlier. Repeat the blurring process to it (but don't desaturate it!). Set it to 10% opacity.
Let's add some texture to it, shall we? Alright, so grab one of these paper textures from BittBox. Open the texture as a layer like we have done previously. Move the layer to in between the light layers. Erase all but the parts where I haven't.
Set the layer to Overlay. Lower the opacity if needed.
Alright we are almost there! Yay! Now let's add in this image of the moon via Google:
Open it as a layer in our composition. Shrink the size of it down to about the size of our comet. Get out the burn tool and burn the side of the moon facing away from the explosion.
Now let's make our moon interact with the explosion a bit more. Use the eyedropper tool and select one of the main colors from the explosion. That turns out to be a blue for me. Right click on the moon layer, and select Alpha to Selection. Create a new layer. Use a soft brush to paint a cresent shape with our selected color. Be sure it is facing the explosion. Duplicate the cresent layer. Blur it with Gaussian Blur by 8 or so.
Now you are done! Enjoy.