Brighter Eye

Great telescopes such as the 200-incher on Palomar Mountain were designed for gathering faint starlight from a wide area and concentrating it in an image bright enough to make a photograph in a practical length of time. The limit of this method has probably been reached; big telescopes are wickedly expensive and hard to build. So forward-looking astronomers are now looking for other ways to brighten a telescopic image.

A promising new method uses an "electronic screen intensifier" developed at Johns Hopkins by Dr. Russell H. Morgan and Ralph Sturm. Primarily intended for brightening the faint images on X-ray fluoroscope screens, it is based on the image-orthicon tube used in television cameras. The tube scans (in 1,029 "lines" instead of the standard 525) the image and turns it into fluctuations of an electric signal.

Faint Shadows. In an ordinary TV setup this signal would be far too weak to be turned back into an image on the face of the picture tube, but Morgan and Sturm have learned how to amplify it enormously. They can put their apparatus to work watching a fluoroscope in a darkened room; it can see in light ten times too dim for human eyes. The faint shadows may be barely visible, but when they appear on the picture tube, they are bright enough to be studied in full daylight. This is important for doctors who examine patients by fluoroscope, and also important for the patients; doctors can now step down the power of X rays needed to get a good, clear picture.

Soon after the scientific world heard about these medical experiments, astronomers realized how useful the screen intensifier might be in their business, especially for viewing the planets. The limiting factor in taking pictures of Mars, for instance, is not the efficiency or magnifying power of the telescope. It is the wobbling of the image because of irregularities that are almost always present in the earth's atmosphere. If the plate is exposed for more than a small fraction of a second. the dancing image blurs the picture with movement.

Promising Canals. The human eye, which sees continuously, sometimes catches Mars through the telescope when its image happens to be standing still for a second or so. Then the observer sees a fleeting vision of the Martian surface, covered with fascinating, intricate detail.

He cannot record what he sees, however, since the eye does not store an image and the brain does not act fast enough to remember it accurately. This is why astronomers do not agree about the famous Martian canals. Some have seen them; some have not, even in years of trying. No one has ever taken a photograph of them.

Last week at the Lowell Observatory, Flagstaff, Ariz., Astronomers Albert G.

Wilson and Earle Slipher predicted that the image intensifier would break the Mars deadlock. Last summer when Mars came close, they attached the tube, still imperfectly adjusted, to their comparatively small 24-in. telescope. Even though the "seeing" was extremely bad during the whole period of observation, they got pictures of Mars almost as good as the best ever taken.

The pictures show no canals or other fine detail, but when the image intensifier was first attached to the telescope, Astronomer Wilson pointed it at Mars and threw the brightened image on the picture tube's face to look at it visually. "Suddenly," says Dr. Wilson, "there were canals all over the place. I had been a canal agnostic, but I am not one any more."

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