ISO amplifies the light signal captured by your camera's sensor.
ISO amplifies the light signal captured by your camera's sensor. Shooting at a higher ISO Means that the camera will have to make some ‘guesswork' as to the detail of the image, which creates ‘noise' and grainy images, but in general, you'll need a fairly high ISO when photographing the night sky unless you are photographing the moon, which is a bright object that emits enough light to enable you to use a lower ISO setting.