In most sciences, artifacts are things to be avoided. Unless you’re an archaeologist, you do *not* want artifacts in your data. Case in point: I was playing around with the Microsoft WorldWide Telescope when I ran across this image, sitting out between Sirius and Orion. If you look closely, you can see that it is an image of a brightening sky and multiple super-imposed images of the instrument package of a large telescope. I don’t know which one, but with all the clutter there, I’m thinking it has to be a fairly big one.