In May and June of 1999, Mars was close to Spica in the constellation Virgo. When I checked the movement of Mars using the program Skyglobe, I found that Mars would move close to Spica in early June and then move "backwards" as it began a retrograde loop. On May 19 I started a series of photos to record this phenomenon. All the photos were taken on Kodak Gold 800 print film using an exposure of approximately 10 seconds with a 55 mm lens at f/2.
The negatives were scanned and a small part containing Mars and a triangle of stars was cropped from each image. The triange has Spica at its lower right corner and 74 Virginis at its upper left corner. A plastic template was made showing the four stars in the triangle and the size and orientation of each image was adjusted so that the triangle was always the same. The rectangle cropped from the negative was always the same size, 100 x 115 pixels. Having a fixed pattern of stars from image to image makes it very easy to see how Mars moves relative to the stars.
One last bit of image processing was to reduce the color variation from picture to picture. Most photos were taken between 10 and 11 PM EDT, but some were taken earlier and some were affected by moonlight. It was possible to adjust the color of all the moonlit images except for the one taken on 5/25/99, when the moon was close to Mars and Spica. The pictures taken earlier in the evening were too blue to match to the others, so they were left alone.