Some weeks ago I read an article about how aperture influences the appearance of light sources in a photo. (Sorry I can't find this article anymore.) On my recent vacation I wanted to try this out for myself. One morning at a lake I got a nice scene with low sun, colorful Fall trees and the lake in the back. Although the mentioned article was about lights in night shots I thought the sun might be a nice light source for playing with different aperture values.
My conclusion out of this experiment is that with higher aperture values light sources may look more like stars with beautiful rays, but I also learned a lot about the disadvantages of those settings. It will always be a balance between good image quality and nice looking light sources. As the dark season is just beginning the chance is good that I will take some new night shots within the next months. And then I will play again with aperture values to see how it influences street lights. Maybe in the dark the dust on sensor and lens will not that much visible.
At last just the other camera settings for both photos. I used my EOS 600D with my EF-S 18-55mm kit zoom lens at a focal length of 18mm. Even it was bright light I chose an ISO value of 200 to get reasonable shutter speeds at high aperture values. The camera was in Av mode with fixed aperture value and calculated shutter speed automatically.