Star Burst

EOS 60D, F/5.6, 1/25s, ISO-800, 18-135 @ 18mm

Just wondering, how can you get a star burst effect on lights at night like the picture above? Does increasing or decreasing the shutter speed get you a star burst or does increasing or decreasing the F-stop will get you there? Been reading and viewing some photographic content on the net. Got the answer but I need to proof it to my self that it is correct... It is more fun to test it out than just believe heheheh, Typical me... 

Tonight I had some time to go out and went to a park near my house. I brought with me only the EOS 60D and EF-S 18-135. Shoot some photos of a street lamp handheld in hoping to find a star burst... So, I took around 6 photos. All photos was taken at 18mm and ISO-800... The first set of photos was taken at different speed but at a constant F-stop... Here is the first set of picture at 1/20s, 1/10s and 1/5s. 

As you can see, nothing changes. The light on the street lamp is still the same with only a small start bust... As the shutter speed is lowered, the star burst is still the same...

The second set is captured with a constant shutter speed. Only the F-stop is changed. Here is the second set...

Aaaaa.... This is more like it... The star burst increases in size as the F-stop is decreased...

Oh ya forget to mention, for proper exposure, when increasing the shutter speed, the F-stop needs to be decreased and vice verse... The pictures above has been edited in Photoshop. I only increased the Exposure and nothing else so that all picture is almost the same.

Oh well. That proofs it that increasing the F-stop does give you the star burst effect... Happy shooting... photos that is...