This results in less light hitting the sensor of your camera, which means that you have to increase your ISO to compensate for it – since you should already be using the widest aperture your lens provides.
As you saw in the previous chapter, to get pin point stars you need to decrease your exposure times. This results in less light hitting the sensor of your camera, which means that you have to increase your ISO to compensate for it – since you should already be using the widest aperture your lens provides.