C&C on my light trail photo please

[JbleezyJ]

I was trying to do star trail photography but I couldn't find something cool upclose to focus on so I turned my camera towards the road and put on bulb mode having the stars move and I was just waiting for a car to pass by on the road. and one did! If I kept the exposure going longer after the car passed by would the photo have gotten overexposed and white? I kinda which I had the stars full circle on. After the car passed by I ended the exposure.

 

[Garbz]

You need to take multiple exposures and stack them together. The stacking method to make the stars rotate without increasing the brightness of the background is to use the "max value" for stacking.

The stars will always be a max value so when you stack your pictures they will show up, but the sky's max value will be the brightness of an individual picture and won't increase in brightness due to the stacking process. For an example here's a photo with much longer startrails http://farm2.static.flickr.com/1353/773160897_fae20200db_b.jpg taken 4km from the city centre of a city with 2million people in it. It is made out of 240 30 second images.