Intro
I see a lot of Milky Way images on social media and one of the most common questions you see in the comments is 'what settings did you use?' or even newbies asking 'What settings shall I use?'.
It's great to see so many people wanting to learn and progress their photography but simply knowing what settings other photographers have used won't always yield good results in other situations. It's best to try and gain a further understanding of why the equipment and settings were used.
There are many factors that effect astrophotography; location, environmental factors, camera sensor, lens and shutter speed. I'll be going through the importance of each one in this post.
Equipment
Now a lot of photographers will often say it isn't the camera but the person that takes a good picture. This is true in regards to having a good eye for light and composition, however when it comes to shooting the night sky equipment makes a hell of a difference!
Camera Sensor: Rather than just the type of camera it's specifically the sensor that makes the difference, the brand itself doesn't matter. As a rule of thumb the larger the sensor, the more light it will absorb so the better it will be for capturing those epic shots of the Milky Way. So if you can shoot with a Full Frame Camera you're off to a good start. This isn't to say you can't get good shots with smaller sensors but having a larger one certainly helps.
ISO: For shooting in low light you'll need a camera capable of producing clean images at higher ISOs. ISO simply stands for the 'International Standards Organization' which, back in the film days, meant film sensitivity would be consistent across brands. In a digital camera it can be compared more closely to digital gain, essentially how much your camera can boost a signal without creating noise. This isn't as simple as 'the higher the ISO, the higher the noise', it's worth learning a little about signal to noise ratio. I always refer people to the PetaPixel article here.
Lens: Here you're looking at the aperture or F-stop. The lower the F-stop the more light your lens can let in. If you have a lens at F2.8 or lower then great, this will certainly help! This means you won't have to push your shutter speed and ISO to such extremes, reducing star trails and noise. Again it is still possible to capture the stars with a lens that only allows a higher F-stop but the results simply won't be as good in a single exposure.
Tripod: You'll be shooting long exposures to capture the nights sky so be sure to have a solid, sturdy tripod to keep your camera nice and steady.
Remote Shutter/Timer Remote: Although not necessary it can be useful to invest in either a wireless or plug in shutter release. This will allow you to take photos without touching the camera, reducing camera shake and resulting in sharper images. If you don't have a remote you can always set your camera to a 2 second timer.
Milky Way over Two Jack Lake
Lake Louise aligns perfectly with the stars.
Settings
Like I mentioned earlier this isn't as black and white as some people may expect, environmental factors come in to play and settings should always be adjusted until pleasing results are achieved. I won't be giving exact settings but will give an outline of how to choose the best ones.
Aperture: This one's pretty straight forward, on most lenses you want to go as low as your lens allows. If you have an incredibly fast lens, say F1.4, you may want to go up a stop or two simply because your lens may be sharper at F2.0 or F2.2 but will still remain fast enough to capture plenty of light. This is something you'll have to play with and adjust other settings accordingly. How sharp your lens is at certain apertures depends on what lens you have. I shoot astro with a Sigma Art 24mm F1.4 and I find this to be more than sharp enough even wide open.
Shutter Speed: How long you open your shutter for will vary depending on what lens you have and what environment you're in. However the Earth is always moving so if you use too long a shutter speed you'll end up getting star trails. Sometimes this is exactly what you want at other times you'll want pin sharp stars.
To avoid star trails it's a good idea to follow this basic rule:
For full frame cameras - 500/focal length = maximum shutter time. For crop sensor cameras 300/Focal Length = maximum shutter time.
So for example I shoot with a Canon 6D, which has a full frame sensor, and a Sigma Art 24mm F1.4. Which would mean I'd use this sum: 500/24 = 20.83 seconds, to avoid star trails I need to keep my exposure below 20 seconds long.
ISO: We touched on this before, how high you can go will depend on your equipment but I would recommend starting high, ISO 3200 if your camera allows. Then shoot a few frames at higher and lower ISO's to see what works best for your camera, it will be a case of trading signal and noise. With my setup I find I can often get away with ISOs as high as 10,000.
Focusing: This will probably be one of the hardest things to get used to and the technique will depend on your lens. If you have a manual lens you should easily be able to focus to infinity without even turning on a head torch! A lot of beginner astro photographers will use a Samyang/Rokinon lens. These lenses have a hard stop on infinity, you simply twist your lens until it hits this point and it should mean your stars should be in focus. With most lenses though the best way to focus is to use live view and zoom in until you find a bright star. That way you can play with focus until your stars are perfectly sharp.
A panorama shot at Vermilion Lakes in Banff National Park
Environment
Knowing when and where to shoot the Milky Way is as important as having the right equipment to do so.
Light Pollution: This is a big one, the less light pollution you have the better. You'll need to drive away from major towns and cities to get a dark, clear sky.
Milky Way Position: Depending on where you are in the world the Mliky Way core will show at different times of year in different positions in the sky. I use an app called Stellarium to help predict the position that can be downloaded as an app on your phone or computer desktop. It allows you to scroll through dates and times to see where the stars, planets and moon will be at certain times. Photopills is also another great tool to monitor where and when to shoot.
Moon Phases: The moon rises and sets at different times throughout the year. Your best bet is to shoot either when the moon doesn't rise during the night or on a new moon where it won't be visible at all. Again the above apps will help you plan this.
Scout Your Location: To get the most out of your Milky Way shot I would recommend scoping out locations in the day taking note of position and composition. This way you can predict where the Milky Way will be and how your shot will look before you arrive in the dark. This saves a lot of fumbling around in the middle of the night when you can't see!
This article has barely scratched the surface in regards to astrophotography, if there are any questions you have please feel free to add them in the comments below :)