Saturns moon as spotted through Cassini

Here I am comparing an older image of Saturn's ice moon Tethys to an more recent image as captured through the spacecraft Cassini. As we can see the two images are hard to distinguish, but believe it or not, the one on the left was shot in 1988! as the other was shot in 2005. Why am I comparing these two images when it looks like the two are the same? Well they are the same, and they are different. The larger image was shot in a larger resolution and at a much closer distance. This is significant because during Cassini's mission, we were able to get a picture of the moon in the sunlight and by zooming in (which I cannot find, but I know it is there.) we see  two very small moons Telesto and Calypso locked in orbit around Tethys. So why is this image so interesting, exactly?

The point of this is to talk about how much astronomy has changed within the last 20 years. The smaller image was shot while on earth and the other in space! This changes the distance between the light source and the receiving medium. This changes the focal distance and leads to better resolution within our cameras and telescopes. Think of the equation d = (f_1)^-1 + (f_2)^-2 which means that if we have a smaller distance we would need a larger focal length. This basically means, the closer we are, the larger the image. And that is exactly what we see here.