Kit 11: Newtonian Telescope

Kit #11: Newton-style Telescope (2100 yen). The original refractive type scopes (Galileo and Kepler designs) use concave and convex lenses to focus the light at the eye. The drawbacks of these designs are that there’s a limit to how big the glass lenses can get, and that the focal length of the lenses requires that the scope bodies get really long as the lens diameter increases. Newton overcame these problems by using a concave mirror instead of the first big lens. The mirror is placed at the back end of the scope, which effectively cuts the length of the scope at least in half, and it focuses the light onto a second mirror at the front of the scope which then aims the light at the eyepiece lens mounted on the side of the scope. The placement of the eyepiece also makes it easier for the operator to stand to the side to look at the image, rather than having to sit down at the far end of the tube.

The one drawback to Newton’s approach is that the second mirror is right in the middle of your field of view, creating a blind spot at the center of the image. Fortunately, the blind spot is not normally noticeable on the larger scopes.

Gakken’s kit #11 lets you build a little 2″ scope. There are about 20 pieces, and the body of the scope is made of two sheets of stiff paper, held in place to the plastic end pieces via double-sided tape. The kit takes about 1 hour to build, and the only real drawback to the design is that the tape tends to lose its stick eventually. I had to glue the paper together after a few weeks. The scope’s focal length can be changed by sliding the outer half of the scope (the mirror is at the back of the outer half) away from the inner half. The smaller mirror is very intrusive now, blocking maybe 20% of the incoming light. But, of all the kits so far, this is definitely the cutest one for just putting on the shelf and admiring. It’s good for inspecting the moon and that’s about it (I tested it the night I built the kit – magnification of the moon is about 1:1, but it brings the craters into really clear focus, and it’s a lot less shaky to hold by hand than the Galileo scope, Kit #19).

This was the first Gakken kit to be missing parts. A couple of the other kits had some extra parts, but this one was missing a mounting screw for holding a support leg to the base plate. Fortunately, I had a spare screw left over from an earlier kit, and I was able to complete the scope easily enough. So, 1 missing screw from out of the 14 kits total I’d build up to this point; not a bad track record, quality control-wise.

The mook talks about Newton’s original scope and gives a summary of some of Newton’s discoveries regarding light and gravity. There’s an overview of other types of scopes, a map of the moon, a demonstration of using a camera with the kit’s scope, and a look at how to make a concave mirror by hand (polishing, etc.) Additionally, there’s a history of space exploration, a description of a communications satellite, a suggestion for how to colonize the moon, and a look at Gakken’s 3-vacuum tube radio. An author gets to learn how to make a light bulb, and there’s also a look at hearing aid implants. Finally, there’s an article on Einstein and Schrodinger. This mook is very science-heavy and I’d love to see it translated into English. But, there are no suggestions for modding the telescope this time.

The one mod I needed was to make caps to protect the eye piece lens and the interior mirror from dust and cigarette smoke. The wind-up doll’s hat (kit #16) worked perfectly as a lens cap, and I cut out a page from the 101Tokyo Air Fair’s exhibitor’s guide book to make the end cap. The artwork from the guide book was Amano’s painting of Gatchaman. Now, I have Gatchaman glaring at me whenever I look at the scope.

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