Ever wanted to take great photos of stars , but weren't sure how? In this post I'm going to share the secrets of astrophotography. Let's get started with a quick look at the two types of star photography .
The two types of astrophotography shot
If you've seen photos of the night sky the chances are that you have seen a couple of styles. One will be a shot where the stars are captured in motion, forming great lines across the sky.
The other will be a static shot of the night sky, perhaps highlighting a constellation or the glow of the Milky Way. I'll explain how to get both of these styles of shot.
Gear you need for astrophotography
The good news is that you don't need a great pile of gear to get good shots of the night sky. Of course, you can purchase expensive long lenses, self tracking tripod heads and so on, but to start with, your gear list should look a little like this:
A tripod. Photos of the stars require your camera's shutter to be open for a time period measured in seconds, and you won't be able to hold your camera still for that long!
A remote release. If you want to shoot for longer than around 30 seconds on most cameras, you'll need a cable to allow you to release the shutter remotely. Some cameras with built-in wifi, such as my Canon 6D, allow you to do this via a smartphone app.
A camera with fully manual controls and a “bulb” mode. For the static Milky Way style of photo, you are likely going to need a camera that performs well at ISO ratings between 1600 and 6400.
A wide-angle lens with a fast aperture rating, ideally between f/1.8 and f/4, in order to let the maximum amount of light in.
A flashlight so you can see what you are doing as well as for light painting. If you put a red filter over the bulb, you'll not lose your night vision when using it to adjust settings on your camera.
A star chart app for your smartphone to help you figure out the location of important stars.
Spare batteries, warm clothes (if it's cold), and some patience!
Getting the shot: Camera setup
Whatever style of shot you are going for, there are some basics that you need to be aware of in terms of setting up your camera. These are:
Shoot in RAW. You should always shoot in RAW anyway, but for astrophotography this will help give you more control when editing your photos later, particularly for noisier images at higher ISO ratings.
Set the camera to manual focus. It will be most likely to be too dark for your camera to focus by itself. If your camera has a live view, you can focus manually using the screen.
Set the camera to bulb or manual mode, so you can control the exposure yourself. You'll want as wide open an aperture as possible in order to let as much light in as possible.
Disable long-exposure noise reduction, if this is an option in the camera.
Astrophotography: Capturing a static star field
Shooting a static shot of the stars requires, I'm afraid to say, a little bit of math. This is because the stars are always in motion, due to the rotation of the earth, and so it's important that you know how long you can open your camera's shutter for before the tracking of the stars ruins your shot.
The math is very simple thankfully — you use something called the rule of 600.
First, you need to know the focal length of your lens, a number measured in millimeters. Then, to calculate the maximum exposure, you divide the number 600 by the mm length of your lens. The resulting number is the maximum number of seconds you can expose the shot.
Let's say you are shooting with a 17mm wide-angle lens. The 600 divided by 17 is 35, which means the maximum exposure you would want to go for would be 35 seconds.
Those 35 seconds might sound like a long time, but there is very little light at night. This is why you need a lens set to a nice wide-open aperture, as well as a high ISO rating, between 1600 and 6400 usually works well.
After all that, getting the shot is relatively easy! Just point the camera at the sky, get the focus right, and take the photo. The hardest part is likely going to be the composition, as it's going to be dark. As with any photo, composition is key to a great result. Some tips:
Find something interesting in the foreground, like a tree line or other natural feature.
If the Milky Way is out, this can be a subject, as well as offering a natural leading line.
Don't forget that portrait orientation can be a great way to give a sense of scale, particularly if the Milky Way is out.
Try using your flashlight on nearby objects to illuminate them and provide interesting foreground subject matter.
You will likely need to experiment with your ISO and shutter speed settings in order to get the best results, as well as trying different compositions to see what works well.
Astrophotography: Capturing star trails
Star trails are a more accessible form of astrophotography, particularly if you have a camera which doesn't perform so well at higher ISO ratings.
The basic principles are the same, except you won't need to worry about the stars tracking or doing any maths. In terms of composition, the same rules apply in terms of finding interesting subject matter, with some additional considerations:
Calculate the movement of the stars so you know which direction your trails are going go in. If you are in the northern hemisphere, the stars rotate around the North, or Pole Star. With a wide angle lens, you can create large circular effects by putting the pole star in shot.
A remote release is even more important, as you aren't going to want to hold your shutter button down for prolonged exposures.
If you have an intervalometer, use this to take multiple shots over time, rather than one super-long exposure shot. Taking a two to three hour exposure can result in very speckly images as the sensor creates what are known as hot pixels. Multiple images can be stacked together in software to create trails after the shot, and you don't run the risk of a flat battery losing your shot.
Shots from around 30 seconds to 4 minutes are likely going to be best, with no gap between shots. Disabling long exposure noise reduction is critical to ensure you don't have gaps between the stars.
Set your ISO value to as low as possible in order to reduce noise.
Take some test shots at higher ISO ratings to ensure your composition is good before you set off a longer exposure.
And that's it for astrophotography. Many of the rules above work for other types of long exposure photography at night, including shooting moving vehicles. As always, practice and experiment until you are happy!