This then, briefly, is how the Sun, or other source of light, makes an image, how the image is fixed on a dry plate, or film, and how a picture is printed from the negative, and having found out this much let’s see how we can make it do a little star work for us.
There is not much we can do in the way of making pictures of the things in the sky with a small camera, but the few things we can do are mighty interesting, and show the stars in a way you can never see them with the naked eye.
To make star trails is one of these interesting things. First, set your camera on a tripod, or other firm support, and focus it on a tree or something as far off as you can see it in the daytime. Now, on a dark night, when there is no Moon, set your camera so that the lens is pointing directly at the North Star, as shown in [Fig. 180]. Set the shutter of your camera for a time exposure and open it.
Fig. 181. Star Trails.
You can go to bed now and let the stars work for you while you sleep, that is if you can get up before daylight the next morning, but if you cannot do this stay up as long as you can, three or four hours, anyway, before you close the shutter.
Now, when you develop the plate, or film, and make a print from it you will have a record of the apparent path of the stars, as shown in [Fig. 181], but which is, of course, due to the Earth turning round on its axis. If you set your camera with the lens pointing toward the ecliptic, that is, the path of the Sun, the star trails will be long, straight lines, and this will make another interesting record.
By pointing your camera toward that part of the sky and during that time of the year when there are showers of meteors, and opening the shutter of your lens, you stand a chance, though it is not a very fat one, of catching one of these wily shooting stars on your plate, and if you do succeed—well, you will have a picture that is a curiosity.
You can photograph the Sun with an ordinary camera and make his disk as large as you want to, but you will get nothing more on your plate than a white spot. The Moon can likewise be photographed, but if you focus it sharp on the plate it will not be much larger than a mere point of light, and if you get a disk large enough to see there will only be a small white spot on your finished print.
To make good photographs of the Sun, Moon and planets, a big telescope driven by clockwork to offset the turning of the Earth is needed. Such a telescope is called an equatorial telescope, and when it is set so that an object in the sky is in the field of view, it will remain right there as long as you want it, and when you make a photograph of the object it will be as sharp and as clear as though both it and the Earth were standing perfectly still.