My new telescope works a great deal better than my first one. We had to exclude about half of the light by putting a piece of pasteboard with a hole in it in front of the object-glass, which has a diameter of two inches, and a focus of sixty inches. It magnifies the moon about forty times, as near as we can judge. How can I tell exactly how many times a glass magnifies?
How many of the other boys have tried to make a telescope according to the directions given in Young People No. 1?
How can I make a cheap camera obscura?
Is it injurious to the eyes to look at the moon through the telescope without smoked glasses?
Olaf T.
The oculist from whom you obtained your lenses will tell you their magnifying power.—You do not need smoked glass when looking at the moon.—A simple form of the camera obscura (dark chamber) is a box furnished with a lens whose focal length is equal to the length and height of the box. At the opposite end of the box from the lens a mirror is placed at an angle of forty-five degrees, from which the image received through the lens is reflected upon a piece of glass, the under side of which should be ground, placed flat directly above the mirror. The image will of course be inverted. It will be more distinct if the ground glass be shaded from the light.
George L. R.—You will see by the letter of Alice Paine in this Post-office Box that she did give her right address. Why your letter miscarried we can not explain.
H. Scott.—Send your full address, and we will gladly publish your request for exchange.