1 00:00:00,010 --> 00:00:12,060 Music 2 00:00:12,080 --> 00:00:16,070 Narrator: I am going to walk you through how to build a simple cardboard 3 00:00:16,090 --> 00:00:20,080 telescope. The body of the telescope is made from two cardboard tubes 4 00:00:20,100 --> 00:00:24,100 that nest together. Here we have a plastic cap, an optional cardboard 5 00:00:24,120 --> 00:00:28,170 washer of about the same diameter, and a convex lens, also of the same diameter. 6 00:00:28,190 --> 00:00:32,190 For the other end of the telescope, we have a piece of foam with a hole in it, 7 00:00:32,210 --> 00:00:36,210 a cardboard spacer sized to fit inside the piece of foam, and another smaller 8 00:00:36,230 --> 00:00:40,230 convex lens. First we will construct the objective 9 00:00:40,250 --> 00:00:44,300 end of the telescope, which points at the thing you want to look at. 10 00:00:44,320 --> 00:00:48,320 Start by placing the plastic cap on a table with the small lip 11 00:00:48,340 --> 00:00:52,360 on the bottom. If you have a cardboard washer, put it inside the cap. 12 00:00:52,380 --> 00:00:56,390 The lens is curved on one side and flat on the other. You 13 00:00:56,410 --> 00:01:00,430 can determine which is which by rocking it gently on a soft surface, trying to touch only 14 00:01:00,450 --> 00:01:04,510 the edges if possible. You will want to put it inside the cap with the 15 00:01:04,530 --> 00:01:08,560 curved side down. You should then fit the cap onto the end of the larger tube. 16 00:01:08,580 --> 00:01:12,610 Now we want to construct the eyepiece end of the telescope, which is the end you 17 00:01:12,630 --> 00:01:16,660 will look through. Start by placing the piece of foam 18 00:01:16,680 --> 00:01:20,700 down on a the table. Put the cardboard spacer into the hole in the foam and 19 00:01:20,720 --> 00:01:24,750 push it all the way down, until it's flush with the bottom of the hole. 20 00:01:24,770 --> 00:01:28,790 Music 21 00:01:28,810 --> 00:01:32,810 The small lens may also be curved on one side and flat on the other, but it's much 22 00:01:32,830 --> 00:01:36,830 easier to tell in this case. 23 00:01:36,850 --> 00:01:40,900 Push the lens down into the hole on top of the spacer, 24 00:01:40,920 --> 00:01:44,970 this time with the flat side down--if there is one. Now put the small end of the telescope 25 00:01:44,990 --> 00:01:49,000 down over the foam piece so it's all flush on one side. 26 00:01:49,020 --> 00:01:53,030 Since you will probably be using your telescope indoors, one of the best things 27 00:01:53,050 --> 00:01:57,050 to use to experiment with focus is a clear light bulb. 28 00:01:57,070 --> 00:02:01,080 To do this, you should replace the eyepiece end of the telescope with 29 00:02:01,100 --> 00:02:05,080 a piece of white tissue paper, held in place with a rubber band. 30 00:02:05,100 --> 00:02:08,100 Music 31 00:02:08,120 --> 00:02:12,120 Point your telescope at a clear light bulb and look at--not through-- the tissue paper. 32 00:02:12,140 --> 00:02:16,140 By sliding the smaller tube in and out of the larger tube, you can bring an 33 00:02:16,160 --> 00:02:20,160 image of the light bulb's filament into focus on the tissue paper. 34 00:02:20,180 --> 00:02:24,240 Because of the simple nature of these telescopes, all of your images will appear to be 35 00:02:24,260 --> 00:02:28,260 inverted. 36 00:02:28,280 --> 00:02:39,890 Music