The brightness of the photo depends upon the aperture level and shutter speed of the camera.
The diameter of the aperture (in the sense above) which restricts the width of the light path through the whole system. For a telescope, this is the diameter of the objective lens. e.g. a telescope may have a 100 cm aperture
Something which restricts the diameter of the light path through one plane in an optical system
An opening; an open space; a gap, cleft, or chasm; a passage perforated; a hole; as, an aperture in a wall
The diameter of the exposed part of the object glass of a telescope or other optical instrument; as, a telescope of four-inch aperture
The diameter of the aperture (in the sense above) which restricts the width of the light path through the whole system. For a telescope, this is the diameter of the objective lens. e.g. a telescope may have a 100cm aperture