What observational technique is used to engage more sensitive rod cells when viewing faint structures?

Looking slightly beside the object (Averted vision)

When an observer is using a telescope and still perceives only gray or near-invisibility when looking directly at a faint nebula, a technique known as averted vision can significantly enhance detection. This method involves purposefully directing the gaze slightly away from the target object, so that the faint light falls not on the very center of the retina (the fovea, which is dominated by cones), but onto an area slightly peripheral to the center. This area houses a higher concentration of the light-sensitive rod cells. By engaging these more sensitive rod cells, the observer can often succeed in turning a near-invisible smudge into a faintly discernible patch, making structure visible even when color perception is impossible.