I have a problem with my Canon 5D Mark II. I was doing some astrophotography and long exposure pictures of star trails. After downloading them I noticed that there were stationary red, blue, green, and white dots. The more noticeable red ones were in the same place no matter where I had the camera pointed in the sky. I went back and looked at previous pictures I took, including a 5 second exposure portrait of someone sitting in a room with natural light, and when I enlarged the image the red dots were also there in the same place. I ran some tests and the red dots become brighter and more noticeable the longer the exposure and are consistently in the same place. They are even faintly visible at 1/40 to 1/50 of a second. Cleaning the lens had no effect. What can I do about this and what may have caused it?