One of the challenges of capturing beautiful photos of the night sky is to get the shot perfectly in focus.
Though modern cameras have incredible autofocus systems, they rely on light to obtain their focus. That means that when you're out shooting stars at night, the camera's autofocus will constantly hunt for the contrast it needs to determine the focus of the shot.
Without being able to rely on autofocus, you'll have to take the reins and focus manually to get clear, sharp photos.
The question is, how do you do that?
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Certain Gear Helps
First things first, you need a lens with a large aperture.
The larger the aperture, the more light the lens can collect, and that makes focusing at night much easier.
You don't have to spring for something like an f/1.2 or f/1.4 lens (though that would be great!). If the budget is a concern, a f/1.8 a f/2 or even a f/2.8 lens should do the trick.
Additionally, you want a sturdy tripod that gives your camera a nice, stable base for shooting the photos.
After all, it won't matter how well you've focused the shot if the camera isn't stable to take the photo!
Follow This Procedure
Before I outline the different ways you can focus your lens at night, it's important to note a few basic steps you'll use regardless of the focusing method.
Once you have your camera and tripod set up, you'll need to switch your camera or lens to manual focus.
Ensure you're using a large aperture - f/2.8 or lower - and set the ISO to about 3200. Again, this helps let as much light into the lens as possible and increases the sensitivity of the sensor to light as well.
Using Live View, zoom in on a bright object as closely as possible. While watching the LCD, manually adjust the focus as needed until the subject is tack-sharp.
Once you've got the image in sharp focus, lock down the focus ring with gaffer's tape. You can then adjust the camera positioning as needed to compose your shot.
Manual Focusing Method #1: Pre-Focus
Photography is all about preparation, and this method of manual focus requires some forethought.
Rather than waiting until dark to acquire focus, you can simply pre-focus your lens ahead of time.
Using this method, you can actually focus the shot using autofocus, but you have to be sure to lock the focus in place. This can be done by switching your lens or camera from autofocus to manual focus once you have the desired focus set.
It's important to note the distance marking on your lens when you're focused at infinity. This will help you reacquire the proper focus if you accidentally move the focus ring. As noted above, a better idea is to use gaffers tape to hold the focus ring in place.
Though this is perhaps the easiest method of focusing for night photography, the drawback is that you can't easily refocus the shot later on if need be.
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Manual Focusing Method #2: Get Help With Artificial Light
Using an artificial light source is helpful because it obviously gives your lens the light it needs to help you acquire focus.
This can occur in two different ways.
First, you can focus on a distant light source, for example, light emanating from a light pole in the background of your shot.
Assuming the light is sufficiently bright and far enough away (so that you can focus at infinity), this can be a hugely helpful method of getting the focus right in your shots of the night sky.
Another way you can utilize artificial light is to use it to light paint in the foreground.
This method doesn't do you much good for focusing on distant objects like stars.
However, if you focus stack your images, you can use a flashlight or a headlamp to illuminate the foreground to get a sharply focused image that you can blend with one you previously took of the sky.
My headlamp of choice is the Petzl NAO + (shown above) because it offers tons of versatility and is a durable rig to boot.
It puts out 750 lumens - more than enough for light painting - so you can create dreamy foregrounds for your astro images.
And not only is it incredibly comfortable to wear, but it also has smart features that make it more functional, too.
In particular, the MyPetzl Light App allows you to keep track of things like battery power, and if you're running low, you can make adjustments to the performance of the headlamp to extend the battery life. Crazy, right?!
The NAO + also boasts a handy feature called Reactive Lighting, which allows the headlamp to instantaneously adjust to the ambient lighting conditions, that way you have just the right amount of light for your photography exploits.
That makes it the perfect choice for light painting and other photography adventures at night!
Either way, if you use an artificial light source to help you get the light you need to focus the shot, it's advantageous to have a lens with an aperture of at least f/2.8 to collect as much light as possible.
Manual Focusing Method #3: Focus on a Bright Star
If there's no objects immediately in the foreground of the shot, you can simply use a bright star for acquiring the focus.
To make things easier, you should pre-focus the lens to infinity, as outlined in the first method above. This will at least get you in the neighborhood of having the shot in focus.
That's important because there will be a lot of noise in the shot, so making out stars can be difficult to do.
Using the camera's LCD, zoom in on the brightest star you can find, making adjustments to the focus ring as necessary to bring the stars into focus.
When you think you've got the focus down, take a photo, then review it to make any exposure adjustments. Take additional practice photos until you have a good exposure.
Be sure to zoom in on the images you take to double-check the focus of the shot, refocusing as needed.
If it seems like a complicated process, it really isn't, especially as you get some practice.
In the video above, Greg Benz offers more details about each of these focusing methods and shows you a live demo of how to manually focus at night.
Now all that's left to do is find a dark spot, set up your gear, and set about getting sharply focused images of the stars.
Editor's Tip: For more tutorials on astrophotography, check out our astrophotography section, sponsored by our friends at MrStarGuy. Learn about composition, camera settings, gear, and other essentials for capturing breathtaking photos of the stars and other celestial objects.