In astrophotography, dark frames are used to capture and later subtract noise from your actual astrophotography images. They help in reducing unwanted artifacts such as hot pixels, thermal noise, and sensor noise.
In simple terms, a dark frame is essentially an image taken with the camera’s lens cap on or with the camera completely covered, capturing only the noise produced by the camera’s sensor. It is captured with the same settings (ISO, exposure time) as your actual astrophotography images but without any light reaching the sensor.
The purpose of taking multiple dark frames is to average out the noise patterns present in each frame, resulting in a cleaner final image. The number of dark frames you should take depends on a few factors such as the ambient temperature, the length of your exposure, and the level of noise you’re comfortable with in your final images.
As a general guideline, taking 5 to 10 dark frames per imaging session is a good starting point. However, some astrophotographers prefer to take even more dark frames for better noise reduction. It’s important to keep the camera settings the same for each dark frame, including ISO, exposure time, and temperature.
Once you have captured your dark frames, you can use post-processing software to subtract them from your actual astrophotography images. This process involves aligning the dark frames with the corresponding light frames and then subtracting the noise patterns from the light frames. The result is a cleaner, less noisy image that better represents the true details of the celestial objects you captured.
Taking and using dark frames may require some additional effort and time during your astrophotography sessions, but they can significantly improve the quality of your final images by reducing unwanted noise.
