Perhaps a bit of clarification is in order for some of the terms used on the Wilson Observatory page:

Newtonian, Cassegrain and Coude refer to the optical configurations of the reflecting telescope. Isaac Newtonian constructed the first functional reflecting telescope, using a concave mirror rather than a lens to focus the starlight. Placing the eyepiece at the mirror's focus would place the observer's head in the way of the incoming light. Newton solved this by placing a small flat mirror, at a 45-degree angle just ahead of the focus, placing the eyepiece at the side of the tube. This is pretty much the setup for almost all small reflecting telescopes used by us backyard astronomers. The Newtonian focus of the large reflectors provides a comparatively small, bright image suitable for direct photography. 

Cassegrain refers to a reflecting telescope design, also of the 17th century, where the flat mirror of Newton is replaced by a second curved (convex) mirror, the light directed back down the tube, through a hole in the primary mirror, to the back of the telescope. The cassegrain configuration gives a much larger, although dimmer, image, more suited to the examination of finer details of small objects. The Mt. Wilson telescopes use a third flat mirror near the back of the telescope to send the Cassegrain focus to the side of the tube, avoiding the need for a hole through the primary mirror. 

The Coude (French for elbow) is a cassegrein setup with the focus two or three times as far from the secondary as the Cassegrain. The light is bounced off a third flat mirror and directed through the Polar Axis, (the axis that allows the telescope to move East-West and follow the sky), to large, heavy instruments located in the "basement" under the telescope, that are much too large to attach to the moving parts of the 'scope itself. All large reflecting telescopes are able to be used in all these configurations, as the observations requires, by switching the various mirrors in and out.

Jack