Hypnotic

New FW document 600 x 600.

Make sure the Ruler is showing (View>Ruler).

Draw guides for the center (using the black arrow tool, click and drag from top and bottom to 300 pixels).

With the black arrow tool selected, set the canvas to a dark color.

Select the Circle tool - go to Properties and set the fill to white, make sure no stroke.

Click and drag from the center point (while holding ALT and SHIFT) to get a huge circle, going outside the canvas. In the Layers panel, change the opacity to around 10 or 15%.

Draw the next circle, a little smaller, change opacity to around 30%. Keep going, drawing about 6 more circles. When you're done, you should see layers with white circles in them, like this...

Go to View>Guides>... and click on "Show Guides" to uncheck the selection.

And your final result will look something like this...

If you want different colors, just change the Canvas Color to something else...