A diaphragm in optics, including telescopes, is a thin opaque structure with a central opening.

The brightness of the light.

The optics which direct the light to the slide.

The diameter of the objective lens.

Albert A. Michelson has written:

'Studies in optics'

'Studies in optics' -- subject(s): Optics

'Studies in optics' -- subject(s): Optics

Variously: physics, optics, quantum mechanics, etc.

W. A. Douthwaite has written:

'Contact lens optics and lens design' -- subject(s): Contact lenses, Optics, Physiological optics

'Contact lens optics' -- subject(s): Contact lenses, Optics, Physiological optics