Long Exposure Images
The image shown on the left is of an object in space known as NGC 7000, or North America Nebula. To get to an image like this, it requires a lot of time and a lot of patience. The simple way to put it, is that this one image is made up of hundreds of other images.
The long way to put it, is a little more complex. To capture the light from this far away region in space, you need to take long exposure photos. This means leaving the shutter open on the camera longer than just a fraction of a second. Sometimes only 5 seconds, but you can take as long of an exposure as you want assuming your camera will allow it. By leaving the shutter open, you are collecting more light. These objects are super dim and not visible to the naked eye for the most part. So you really want to collect as much light as possible. The issue with long exposure images is that you start to introduce a lot of noise in the image (noise is the graininess you see in some images). This is due to the sensor of the camera heating up. This brings me to my next point.
Now, why do you need hundreds of images of one object, just to get the image on the left? To mitigate the noise that shows up in a long exposure image, computer software is used to “stack” many images to form one. The software looks at the images and can see where the noise is and averages all of the images together to help get rid of the noise. What is left in the final image is just the object you are photographing. Noise is always completely random so it can never be the same in any 2 images. This is how the software determines what is noise and what is not.
The final step is post processing. This involves adjusting the different levels in the image. Such as the highlights, midtones and darks. This is essential to try and pull as much detail out of the image as possible.
Planetary/Lunar Images
Planetary imaging is much different than photographing deep sky objects such as nebulae or galaxies. Because the moon or the planets are bright, we do not need long exposure. In fact, you want to get the shortest exposure possible, I’ll explain why in a moment.
The main difference in the two types of astrophotography is that when imaging planets and the moon, you should actually take a video of it. Why? Because a video is essentially hundreds or even thousands of very short pictures. The reason you want the shortest exposure possible is because you will have a higher framerate in the video. Which means you get more images in a shorter amount of time.
Once you have your video, you can use another computer program to break down the video into individual images. Now that you have the images, just like with long exposure imaging, you want to stack them together. The software will average them all together and create a single image out of it. From there, you can edit them to make it a little sharper and to bring out the colors. As you can see in the Jupiter image in the bottom right, I was able to get the colors in the cloud bands to come out.
