by Scott

Today we are going to give you a basic night photography tutorial. If you found your way here from the article on the Gaia App blog about night photography, thanks for coming over. For everyone else, welcome. There are many techniques and tricks to get the most out of  your night photography sessions. I am gearing this to those just starting out. I will talk about some night photography basics such as camera and lens selections, compositional ideas, tips for locating the Milky Way galaxy core and the North Star and finally a little more detail on processing your images.
The first thing I want to talk about is long exposures at night. Back in the days of film cameras, we had these little wires called cable releases. You could screw it into the top of your camera, plunge the cable, lock it down and go have a beer or three. When you came back an hour later you would have a single exposure that showed the stars (or headlights, or airplanes) streaking through the night sky. Of course, you wouldn’t know if it was going to be usable until you developed it several days later. Fortunately, with today’s modern digital cameras there is instant gratification. There is also one big drawback – noise! When you leave an electronic sensor activated for prolonged periods of time, it builds up heat and this heat can cause individual receptors to trigger resulting in white, red or blue specs in your image. Another way you increase noise is by turning up the ISO (or sensitivity to light) on your camera. This makes the sensor more sensitive to photons, it also results in increased gain or another type of digital noise. Don’t despair! Even though it seems the deck is stacked against you, there are ways you can make amazingly clear photographs in the darkest skies.

 

Choice of equipment:

The camera and lens setup you chose will have the greatest impact on the quality of your astrophotography. Using a camera with a full-frame sensor is by far the best. The individual pixel lenses on full-frame camera sensors are larger and do not produce as much noise as the smaller individual pixels on a DX or 2/3 crop or APS-C sensor. When choosing the best lens for night landscape photography you want a wide angle lens with as large an aperture as you can afford. The aperture is the opening in the center of the lens diaphragm. The larger the opening, the more light gets through. We call the measurement of the size of the aperture an F-stop. To make it extra confusing, the smaller the F-stop number, the larger the maximum opening. An f/2.8 lens lets in quite a bit of light. An f/1.4 lens will let in 4-times as much light. More light is better. Even an f/2 lens lets in twice as much light as an f/2.8. You can see where I’m going with this right? The more light you let in, the less you have to crank up your ISO in order for the camera to record it. The less you crank up your ISO, the less noise your image will have. My favorite lenses for nighttime landscape photography are a 20mm f/1.8 and a 24mm f/1.4. I prefer fixed length lenses to zoom lenses as their simpler design produces sharper images, not to mention they are a lot lighter if you are hiking around. Now scroll down to have a look at a few images with long exposures at night:

 

What the above images have in common are long, streaking star trails. To get this effect in modern digital cameras, you need a few extra steps. Remember earlier when I said that back in the film days we just left the shutter open for an hour or so to get this effect? If you do this with a digital camera, your image will be completely full of blue and red specks from the heat generated by the sensor being on. Not to mention it will suck your battery dry in no time. Fortunately there is a simple way to get this effect, image stacking. For that, you need Adobe Photoshop or comparable software. Using a tripod, take a series of images at 30 seconds exposure, one immediately after the other. Many cameras have intervalometer functions built into them, so refer to your camera manual. This allows you to tell the camera to take a series of, say 60, 30-second images one right after the other. Once you bring these images into photoshop you can use a Photoshop action to load images into a stack, or if you use Lightroom to process the images, you can right click (or control click on a Mac) and chose Edit In>Open as Layers in Photoshop. Once you have the images all neatly stacked into layers in photoshop, you are going to change the blending mode for all of them to “lighten.”  What a lighten blending mode does is only allow areas that are lighter than the layer above it to show through. Assuming you have your camera on a tripod, it’s nice and dark and somebody doesn’t shine a bright light in the middle of your photo on image 27, the only things from image to image brighter than what came before are the stars, since they are traveling through the night sky. For bonus points, learn how to locate the North Star. The North Star is the star around which the entire night sky rotates. In the image above of the petroglyphs pointing directly up at the north star, all the rest of the stars create a circle around that point at longer exposures adding drama and flow to your composition. There are some apps I will mention later that will help you locate Polaris, the North Star. But the easiest way is to find the big dipper. From the front of the dipper (looks more like a pot to me.) There are two stars that form the front of the pot. If you extend that imaginary line of the front of the dipper or pot up about the same distance above the dipper as there is between the two stars that make up the front of the pot, you will see a faint speck. That is Polaris.

 

To Moon or Not to Moon:

The moon is awfully bright. If you go out to photograph the night sky with more than roughly a 1/4 moon up, your stars are going to get washed out. On the bright side (literally) shooting under the moon with a long exposure looks about like shooting in daylight. You can make this work to your advantage. The image of me standing in the middle of “The Wave” in Utah under a full moon is a great example for this. I wanted a shot of the wave with crisp colors and no shadows. Unfortunately of all my many attempts, the only time I was lucky enough to draw a permit was in early Fall. At that time, the sun is still a ways to the south and no matter what time of day I tried to shoot this image, there was always a distracting giant shadow across the bottom of the wave. Fortunately, the full moon was right over head that night, so all I had to do was wait until 10pm or so until it was directly overhead and take the picture. Under the full moon, it looks as clear as daylight, but with some interesting stars as a bonus. The image of McWay falls below is a similar concept. The photographs below of the milky way above Bonsai rock in Lake Tahoe, and of the stars over the moving rocks in the Racetrack area of Death Valley National Park were intentionally shot when the moon was just under 1/4 full. With only a small slice of moon in the sky, you still get a good amount of detail illumination in your foreground, but your stars pop out more because the sky is darker. In the image of delicate arch at Arches National Park in Utah, and of Thunderbolt Peak in the High Sierra, I timed my photograph to coincide with the setting of the moon. You know how when you are up at sunrise or sunset and you watch the beautiful red first light hit the tops of the mountains, (or last light if it’s at sunset.) The moon does the same thing. It casts a gorgeous deep red glow on the landscape as it first comes up, or just before it sets. It’s so dark your eye won’t see it, but trust me, your camera will!

 

 

Put a person in there:

Adding people to your landscape photographs can give a sense of scale. The same goes at night. The only difference is, at night, you have more time to play around. Light up a tent, paint a rock with your flashlight while you are taking that 30 second exposure, stand still with a headlamp pointing at the sky, run around with that same headlamp and make lots of playful light streaks. The world is your oyster!

 

But how did you get the stars so sharp:

A big trend in night photography is NOT to show the movement of the stars. Instead, we make the stars and the milky way galaxy the focal point of the picture, or use it as a compositional element. In order to do this, you need the fast gear mentioned at the beginning of this post. In addition to the right equipment, there are a few rules to follow. In general, you will start to see movement in your stars at a shutter speed any slower than 500÷focal length of your lens.  So if I am using a 20mm lens, the longest exposure I can have is 25 seconds (500÷20=25.) In reality, a lot more goes into this than just the length of your lens, but if you want to geek out on math, or get an app that will do this all for you automatically, check out this star spot calculator from Photopils.

Apps like Photopils, The Photographers Ephemeris and Go Sky Watch will also help you locate the center of the Milky Way. They are also great at helping you find the North Star, or letting you know when and where the moon or sun will rise and set. The Earth is located on the outside of one of the spiral arms of the Milky Way Galaxy. When you compose your shot so you are looking back toward the center of our galaxy, that is where you see the large, nebulous area of stars that is so beautiful. You can see obvious examples in the images below. Otherwise the night sky is just a bunch of pinpricks of light without much focus. In the Northern Hemisphere, the Milky Way core is visible from roughly March through October.

 

Now to go into a little detail about processing your night sky images. Here are some general settings I find myself using when shooting at night, just to give you a starting point. It will be different depending on your camera and lens setup. I shoot a lot at f2 ISO 2000 or 2500 and a 20 second shutter speed. I may shoot a frame at 20 seconds to freeze the stars and another at 30 or 45 seconds to get some detail in the foreground, then blend those together in Photoshop. There is a useful technique to help eliminate hot pixels from your frame called dark frame subtraction. Basically, when you are done with your shoot, put the lens cap on before you pack it in and fire one frame at the exact exposure you were using for your night images. That frame will be black. You can then bring that frame into photoshop. Layer it with your night shot (make sure the orientation in the same) blend using “difference” mode and viola, any hot pixels from your photograph will disappear. You must use the same exposure settings, and your camera must be at the exact same temperature as your image frame for this to work.
Some of us may not have fancy full-frame sensor cameras. Or even if we do, we may want to get a really low noise image to blow up huge. The way to do this is by Exposure Stacking your night shots. This is a much more complex process and requires Photoshop and Lightroom.  You can follow this link to learn more about exposure stacking night photography.  One final thing that should go without saying, always shoot in a RAW image format. Most of these techniques won’t work with already processed JPG image files. You need raw, unprocessed data for best quality.