How the New 200 Inch Telescope Works
April 1938 Boy's Life

Drawing of Hale 200" Telescope in April 1938 Boy's Life - Airplanes & Rockets

Fig. 1 - Drawing of Hale 200" Telescope at Mt. Palomar

Hale 200" Telescope in April 1938 Boy's Life - Airplanes & Rockets

Figure 2 - Artist's Concept of Hale 200" Telescope at Mt. Palomar

Cover April 1938 Boy's Life - Airplanes & Rockets

The [George Ellery] Hale 200−inch telescope saw first light (first official observation) atop Palomar Mountain, in southern California, on January 26, 1949. That was a decade after this early report on its planning appeared in a 1938 issue of Boy's Life magazine (the official publication of the Boy Scouts of America, BSA). It held the title of the world's largest telescope until Russia commissioned its 605 cm (238 in.) BTA-6 in 1976. As of this writing, the telescope with the largest light collecting capacity is the Large Binocular Telescope (LBT) on Mount Graham, in the Pinaleno Mountains of southeastern Arizona. When using both 330 inch mirrors, the LBT has the same light-gathering ability as a 464 inch single telescope and the resolution of a 897 inch wide one.

How the New 200 Inch Telescope Works

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.

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.

Here is an ad on my RF Cafe website from the May 1948 Saturday Evening Post magazine pitching the 200" Mt. Palomar Telescope Pyrex Mirror Blank by Corning



Posted April 12, 2024
(updated from original post on 5/5/2012)