The second is an automatic cleaning system, using either tiny windshield wiper-type arms or a high-pressure spray to keep the front lens clean.

Only the two front lenses were to move when focusing.

"Just stand by," directed his friend, clamping his green disk over the front lens, or objective, of the telescope and turning on the current.

Finally, the front lens is a photographic or cinema lens that projects the image desired onto the focusing screen.

Behnke switched it on, pulled the cap off the front lens, and adjusted the power setting to its lowest level.

Apparently, it used a distant solid wall as an extension of its front lens.

The worst that can happen is for the front objective lens to break, which usually occurs when the telescope is dropped.

The front lens is well corrected for spherical aberrations but introduces coma.

On the front lens there is a miniaturized mirror the same size as the illuminated surface on the object.

After passing through the specimen the light diverges into an inverted cone to fill the front lens of the objective.