The angle is preferred to be small in high resolution optical instruments to make it more noticeable.
Explanation:
The capability of any device that form image can be an optical or radio telescope, camera, microscope or eye that can distinguish small details in the object is called angular resolution.
This is the main component for image resolution. The accuracy in the measurement with accordance of space is spatial resolution. It is associated with the angular resolution.
The ability of viewing an object in a distinct manner requires smaller angular distance and this is known as resolving power. When we need to view an object in an accurate and in a distinct manner, it is required to be in smaller angle between the viewing objects.