here you see my first try, using a single raw picture. exposure time was about 6 seconds.
(http://farm4.staticflickr.com/3830/10517643766_bd2fa14a6a_c.jpg) (http://www.flickr.com/photos/98369596@N03/10517643766/)
IMG_7850 (http://www.flickr.com/photos/98369596@N03/10517643766/) von Sebiboss (http://www.flickr.com/people/98369596@N03/) auf Flickr