|We are all acquainted with the common telescope in which a series of lenses is mounted in a long barrel, which can be shortened by sliding the segments together. This is technically known as a refractory type. |
In building a giant telescope it is impractical to make a barrel long enough to accommodate the giant lenses. So a system of mirrors is combined with the lenses, and we have what is known as a reflecting telescope. The 200 inch lens of the new telescope described on page 18 is actually a mirror.
Fig. 1 - Drawing of Hale 200" Telescope at Mt. Palomar
At right is reproduced an artist's conception of how it will look set up in the observatory, above is a diagram explaining how it works.
The starlight having entered the open tube is reflected from the 200 inch mirror AA back to a focal point at B. An observer can reach this point of first focus by bridge J (Fig. 2). To send the rays to a second focal observation point D (Figs. 1 and 2) a convex mirror C intercepts the rays from A and B and reflects them down to observation point D, where Fig. 2 shows a platform suspended underneath the 200 inch mirror. The rays arriving at D come through a tube fixed in the center of the mirror. The rays may also be extended from mirror C to E, from E to F, from F to G and from G to H (Fig. 1).
I is another point of focus, and down inside the huge arm (an open section of which is shown) is a chamber for spectographic work. These arms on each side of the tube are parallel to the polar axis. The control board is located at K (Fig. 2). The great housing running at nearly right angles to the telescope is the counter weight to the telescope. It permits the giant apparatus to be moved and aimed With delicate control.
Figure 2 - Artist's Concept of Hale 200" Telescope at Mt. Palomar
Here is an ad on my RF Cafe website from the May 1948 Saturday Evening Post pitching the 200" Mt. Palomar Telescope Pyrex Mirror Blank by Corning
Posted May 5, 2012