There’s a car dealership in Astropotamus’s home town that claims that you can’t stack cars. I’d argue that you can, but it’s unlikely that they’ll be very useful after you do so. But that’s neither here nor there. You might not be able to stack cars, but you can certainly stack stars!!
Actually, we’re talking about stacking images of stars, not the stars themselves. Suppose you took 100 pictures of something from the same place, at the same time, with the same camera, using the same settings. You’d expect the pictures to all come out the same, right? Suppose you were taking a picture of the moon, 250,000 miles away. Not only is it moving, and the Earth is moving, but the air between you and the moon is moving, and the whole set might end up looking quite awful.
Luckily, with computers, there is software that can piece together the best parts of those hundred (or hundreds) of images, and end up with something that looks much better than what you saw with your eye. Sometimes, it’s so much better that it’s just spooky. In fact, this technique is so good, that you can even do it with a web cam that takes dozens of pictures per second. Even though each individual picture might not be perfect, in one minute you can get 1800 images (or more!) that you can stack, resulting in some of the most spectacular pictures of the moon, planets, and deep space objects you’ve ever seen.
This is a common technique for Astropotamuses, since it’s cheaper than getting a really big Time Machine and a really expensive camera and taking really long exposures and putting together really complicated images. It can be frustrating though, since the software is good, but it’s only as good as what it starts with.
For fun, I took a simple point and shoot digital camera, held it up to the eyepiece of my Time Machine, and took about 20 images. I then used a piece of software to stack the images into a single, final image. The edges aren’t as clean as a single image would be, but it’s at the terminator, where light meets dark, that the details are anyway. See what you think about this stacked image compared to some of the ones of the moon you’ve seen here previously.