As a landscape photographer, I typically liked to work at sunrise and sunset. But the night sky holds its own magic, with countless stars, the moon, and the Milky Way all out there waiting to be photographed.
Obviously, all night landscape photography happens on a tripod. What type of shots you go for will depend greatly on your patience. Night sky exposures can range from 15 seconds to several hours, depending on your goals. Star fields can be captured with exposures of about 15 seconds, with aperture and ISO varying depending on the lens in use.
One important thing to be aware of is the available light around you. Any ambient light will diminish the intensity of the stars. This includes the moon, streetlights, a town or city with buildings that have outside lights on, or even just car lights. All of these will have negative effects on the exposure of the night sky. The best thing to do is to find a rural area where there aren’t any street lights, traffic, buildings etc. The stars will be most intense and easily photographed.
Because the night sky is best photographed, well, at night, it will be important to have a flashlight or other illumination to light the way while you hike to your location or assemble your gear. Headlamps work exceptionally well for this. These lights also come in handy for “painting” the foreground with light, to add some extra depth to your images.
In addition to the camera and lens, a remote release, or even better, a time controller is a necessity. The remote release will allow you to trigger your camera without touching it. A timer remote control (such as the Canon TC-80N3) does that and more. When shooting star trails, the timer can be programmed to take as long an exposure as needed. It can also be programmed to take several exposures in sequence if needed. This is helpful for stacking images, a common technique when shooting star trails.
I previously mentioned having a flashlight handy for painting the foreground. Depending on the type of flashlight used, color correction gels can be useful as well. Newer, LED flashlights have a much cooler light source than traditional flashlights, so a warming gel will help make it more natural looking. For lights using traditional bulbs, a cooling gel may be desired. Experimentation is essential here. Too much light will ruin the exposure, too little won’t help the foreground the way that was intended. Generally, a quick kiss of light is all that may be needed. A neutral density gel over the flashlight will help regulate it so just the right amount of light is applied.
One problem with night time photography is the long exposures. Digital imaging sensors generate heat when they capture an image, and that heat manifests itself as noise in a long exposure. Today’s digital SLRs all have settings for long exposure noise reduction. This is generally done through a method known as “Dark Frame Subtraction”. First, the camera takes the image at the intended exposure. For this case, let’s say it’s a 30 second exposure. When long exposure noise reduction is enabled, the camera then takes a second exposure, this one with the shutter closed. The imaging sensor is charged, for the same amount of time as the original exposure. This second, dark frame, is then compared to the first frame taken. Since both frames were “exposed” for the same length of time, the heat generated on the sensor should be the same, and thus the noise generated should be the same. The camera then compares the two frames, and removes the noise that is consistent in both frames. While the camera does this, it is not possible to take another exposure, so this can become a very long process for star trail images that could be as long as an hour or more. Batteries are of paramount importance for this procedure, as the image won’t be recorded if the battery dies before long exposure noise reduction is complete. If your camera has an AC adapter, and a generator or other power source is available, it will make the stress of wondering if the camera has enough battery power go away. If you plan on stacking multiple images for star trails, this feature should be turned off, since continuous images are needed to keep the star trails continuous.