Astrophotography - night time photography

Shooting landscapes during the night creates stunning photos. Our eyes are able to see the night sky in great sensitivity and we can look at the stars and even see the Milky Way in good conditions. 

DSLR and mirrorless cameras have an even greater ability than our eyes and can produce photos at night with fantastic details of the night sky. These photos can be achieved by using the advantages of DSLR cameras like high ISO capabilities, fast aperture lenses and long exposures. Shooting night landscapes also create some challenges we have to deal with like noise and depth of field (DOF) issues which will be discussed in this article.

Shooting landscapes in daylight allows us to use comfortable exposure settings like low ISO,which gives us high quality, low noise and high dynamic range photos. We can also use small aperture settings and gain very large DOF and the shutter can be used in almost any speed we want,from short to long exposures. When shooting at night we have to use much different settings in order to have enough light in our photos.

Astrophotography RECOMMENDED GEAR

Cameras: naturally, cameras that can handle high ISO like Full Frame DSLRs are preferable. Whatever camera you're using, try to learn the maximum ISO you can use and get descent results.

Lenses: wide angle lenses with fast aperture are highly recommended. A wide angle lens will allow you to capture a very wide view angle of both the ground and sky and will also allow long exposure time without smearing the stars. Fast aperture enables more light to enter through the lens.

Tripod: a sturdy tripod is important so the camera will be stable and won't move during the long exposure. Another advantage is a tripod that can get really low and allows you to compose with the camera pointing towards the sky.

Astrophotography exposure and technique

ISO:

Shooting at night forces us to use high ISO settings. From my experience in order to get sufficient exposure you'll need to use at least ISO 800 and higher to get good results (depending also on your lens and moon lighting). Using high ISO makes the camera more sensitive to light, but not without drawbacks.

Problem:
High ISO generates noise. The noise makes the photo grainy and distorts colors.

Solution:
There are two main "solutions" for noise caused by using high ISO. The first is using a high quality camera that can produce photos with relatively low noise like full frame cameras. Knowing the ISO limits of your camera is also important. Most crop cameras can shoot up to ISO 1600 and get a reasonably good photo. Full frame cameras can go up to ISO 3200-6400. The second is to clean the noise in post production with editing software like Photoshop or Lightroom.

Aperture

Shooting landscapes at day time allows us to use small aperture to get large DOF. At night time we need all the light we can get and we usually have to use the widest aperture our lens can offer.

Problem:
Wide aperture causes narrow DOF.

Solution:
In order to get the largest depth of field possible which will include the sky and as much foreground as we can get we will have to use the hyper focal distance. The hyper focal distance is the closest distance we can focus on and still achieve DOF that lasts to infinity. For example, if I use a 14 mm lens with 2.8 F-stop,the hyper focal distance is 2.5 meters. That means I can focus on 2.5 meters and the DOF will start from 1.5 meters and will last to infinity. Each lens (focal length: 14mm, 17mm, 24mm…) and aperture combination has its own hyperfocal distance which can be calculated with a DOF calculator available in the internet and even in a smart phone application.

shutter speed

Using slow shutter speed and making long exposure is one of the best ways we can get more light. Long exposure can generate a little bit of noise but it is very minimal. The bigger issue with long exposure is that earth is rotating on its axis and the sky moves relatively to our position.

Problem:
Stars can look smeared if we expose for too long and won't look like dots. If we don't mind smearing the stars then exposure time can be as long as we want.

Solution:
To get the stars look like dots we have to limit our exposure time. The maximal exposure time depends on the focal length we use. The wider the focal length – the more we can expose.

This is my recommendation for maximal exposure time:
24mm (FF) / 17mm (crop): 30 seconds
16mm (FF) / 10mm (crop): 40 second
14mm (FF): 50 seconds

The times are based on my own experience. Using these exposures you will smear the stars, but it will only be noticeable if you zoom inside the photo. If you want to avoid smearing at all I recommend 5-10 seconds less.

composition in Astrophotography

Undoubtedly one of the most important elements in your photo. In most night photos the night sky will take the major part of the frame so we will usually compose close to the ground and point the camera upwards. Even though we're shooting mostly sky, it is still important to include some foreground with powerful elements that will add interest to the photo and connect us to the ground. Good foreground elements can be mountains, old trees, interesting rock formations, rock arches and more. We will usually compose them at the bottom part of the frame.

outdoor CONDITIONS FOR Astrophotography

If you're aiming to get as much star light possible with minimum interference There are several things that will help you.

milky way photography

The Milky Way is one of the most attractive and interesting elements in night photography. It adds a lot of interest to the background and serves as a central part of the composition of the photo in night shots. The technique of photographing the Milky Way is the same as what you have read so far, what is important to understand the characteristics of its appearance in the night sky.

The Milky Way appears in the night sky throughout the year, but there is a significant difference in its size, brightness and position in the sky during the months of the year. This difference is caused by the relative position of the Earth towards the Sun and milky way during the seasons.

The Milky Way is a relatively round galaxy. Earth's position in the milky way galaxy is approximately halfway between the center of the galaxy and the edge. When you look towards the core or the center of the galaxy there is high density of stars and therefore you see a strong milky way. When you look towards the edge of the galaxy, the density of stars is relatively low and therefore you see a faint milky way (the next explanation is based photographing in the northern half of earth).

The earth surrounds the sun during the year. The change in earth's position towards the sun affects the part we see of the milky way. During the summer nights we look towards the core of the Milky Way and therefore we see it strongly. During the winter we look towards the edge of the Milky Way and therefore we see it weak. In the following images below you can see a diagram explaining earth's position relatively to the sun and  the Milky Way core or edge.

ARTIFICIAL LIGHT PAINTING

If you want to shoot with no moon light to get better lighting from the stars you might need to paint your foreground with artificial light. Light painting can be done with all kinds of light (Flash, led lamps, torches...). To make the lighting amount on your foreground look natural it is important to make several shots and see how much time/how strong you need to do the lighting. I recommend to light the object from both sides to create shadows and make it look 3 dimensional.

If you want to the sky in your photo to look Bluish you'll usually have to choose low Kelvin temperature for the white balance of the photo (2500-3500). Choosing low Kelvin temperature will also make your Foreground look Bluish so it is recommended to light your foreground With a CTO gel on top of the light source to give the foreground a more natural color.