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The Boy's Telescope - Harper's

 

The parson's boys were very fond of astronomy. They knew the chief constellations, and kept the place of the planets as they moved along among the stars. When their father told them how splendidly the moon and the planets look through a telescope, they were sadly disappointed to learn that a telescope costs so much money that he could not think of buying even one of the smallest size. Happening to hint that perhaps one might be made at home at small expense which would show the moon in new light and bring Jupiter's moons to sight, they gave him no rest till he had agreed that he would "see about it."

A few days afterward he showed the boys two common tin tubes which the stove man had just made. One was about one inch and a half in diameter, and about thirty inches long; the other was about twelve inches long, and just enough smaller to slip inside the first, and move easily out and in. The inside of both was painted black, so that there would be no reflecting of light inside. It is better—he told the boys—to paint the inside, if possible, after the tube is made, because the rolling and pounding in shaping and soldering the tube are likely to make the paint crack off. Then he took out of his pocket a paper, and unrolled a round spectacle glass, just big enough to slip into the end of the larger tube. "What's that?" the children exclaimed, all at once. "This is the object-glass of our telescope," was the answer. "The light from the object comes through this into the tube. It is a thirty-six-inch glass; that is, it brings the rays together at a distance of thirty-six inches." Frank held it up to the sun, which was getting low, and when the rays began to burn his hand, Walter brought the yard-stick, and it was just about thirty-six inches from the glass to the spot on his hand where he felt the heat. That was the focus of the glass. While the boys were wondering how the object-glass was to be fastened into the tube, the parson was already doing it. He had the tinman cut slits in the end about an eighth of an inch wide and almost twice as deep. Every other one of these he doubled back inside the tube, and pressed down with pincers, so that there should be nothing sticking out in the way of the moon and stars if they should try to get in. These made a rest for the glass, so that it couldn't slip into the tube. Then he bent the other slits down over the edge of the glass, but not so as to shut out any light, and these slits held the glass firmly.

The boys, of course, now wished to see whether the steeple of the church looked any bigger through this tube and object-glass. They couldn't see it so well as with the naked eye, and feared the new telescope was a failure. But their father told them it was too soon yet to vote on that question. He told Frank to hold out his hand, and see whether the sun would burn his hand through the glass and tube, as it did through the glass alone. It did. "Now," said he, "if you hold this tube up to Jupiter, at thirty-six inches from the glass there will be a very small image of him and his moons. If we could only see that image or picture through a microscope, we might see the moons as plainly as we see Jupiter himself with the naked eye."

"Why won't our microscope do?" asked Walter.

The parson said we couldn't get the image and the microscope together rightly; but while he was explaining, he was also unrolling another paper, out of which came a big bulging glass almost as round as a boy's eye. The edges of this had been ground down so that it would go into the end of the small tube, and it was fastened in just as the other was, only the slits needed to be a little longer, because the glass was thicker. This was a one-inch eyeglass; that is, it must be an inch from the object or image at which you are looking. He then cut in a piece of paper a round hole about as big as a shirt button, and pasted this over the eyeglass, and covered the end of the tube around, so that no light could come in there except through this small opening in the paper, which was so put on that the eye must look through the middle of the glass. He also pasted some strips of brown paper around the other end of the telescope, jutting over the object-glass just enough to keep it from breaking, and to prevent any light from coming through the edges, but not letting the paper touch this glass, as it did the eyeglass. The object-glass wants all the light it can get.

The boys had the first look; but they could see nothing, though the woods to which the glass was turned were yet visible.

"What's the focus of the glasses?" asked the parson.

"Thirty-six inches and one inch," was the correct answer.

The boys marked where the thirty-six inches ended, measuring from the object-glass. They then brought the eyeglass up to within about an inch of that, and looked through it again.

"Oh-oh-oo!" exclaimed Frank: "I see the trees so near that I can get hold of them, but they're bottom side up!"

"Yes," said their father, "but that will make little difference when looking at Jupiter or the moon."

They all had to wait what seemed a long time for the darkness to come, and let the stars appear. When the parson returned from the post-office after tea, he said it would be impossible to hold the tube in the hands steadily enough to see the planets plainly. So he found a strip of board about a foot long and two or three inches wide, which was hollowed out on one side. Into this hollow he fixed the tube by common tacks and small wire. Then through the middle of this strip he bored a large gimlet hole, and put in a long screw, and went to the workshop in the basement to make a standard into which to screw the strip which held the tube. He couldn't find nor make just what he wanted soon enough—the boys said that "Jupiter had just come out clear"—and so he caught the first box he could lay hold of, and screwed the tube upon one of its sides, just tight enough to hold it snug, yet let it move up or down. Then he called for a light stand, and case knives to make it and the box stand perfectly still. He took his place on the portico, got everything ready, and said he was "afraid to look for fear the boys would be disappointed." Frank said he "would like to look," and so, as he had been the most anxious to have the telescope made, his father gave him the first chance to be glad or sorry. After moving the box and the tube a little all kept silent, but soon Frank began a louder "Oo-oo-oo!" than before, and, much excited, exclaimed: "I see 'em: four red bright little fellows, all in a straight line," and then he ran as if half crazy, shouting, to his mother: "We got 'em, mother, all four of 'em! I wouldn't swap our telescope for any other. Come and see!"

The parson too was much delighted. As he happened to look at the other side of the box, he was amused to find that he had mounted his telescope on a "Eureka Soap" box. In a few days he made an upright standard, into which he bolted the telescope just tight enough to hold it, but let it move freely. A common screw becomes too loose in a little while. The instrument cost the parson only forty cents for the tubes; the glasses were given, but ought not to cost more than a dollar or two. If a one-inch eyeglass can not be had, a two-inch eyeglass will answer quite well. The reason for having two tubes is that eyes differ, and that what is bought for a thirty-six inch glass may be an inch or two more or less than that, so that the smaller tube must be moved back and forth till the eye finds where the view is plainest. This instrument shows the moon beautifully. You read of the circular mountains and the extinct volcanoes; here you see them. It is especially delightful to see in the new moon the light breaking over the mountain-tops and through the notches while all the plain behind is yet in the dark. Though it is now a good while since the parson made the telescope, he waits impatiently every month for the new moon to come again.