Kt 19: Galilean Telescope


Galileo Telescope, kit #19 ($20). After getting the Stirling engine, I decided to scour the various bookstores to see what other kits they had on the shelves. Most had the theremin, the synthesizer, the slow clock, and the Edo era static generator. And the big Kinokuniya store north of Shinjuku station had quite a few other kits. But only one little shop in Noborito had kit 19. The telescope preyed on me, so I decided to get it on the way into work, and I spent 2 hours working on it after midnight when I got home that night just to see how it would turn out.

In essence, a simple telescope is nothing more than two lenses – a bigger, convex lens to gather light and focus it to a point, and a smaller one to take the gathered light and redirect it to your eye. Everything else is just window dressing. That is, the metal tube body is just there to hold the two lenses apart from each other, and the tripod holds the scope steady so you don’t get seasick from all the jittering. All you really need to explore space are the two lenses. Galileo wasn’t the first to invent the telescope, but he did improve it to the point where he was the first to see four of Jupiter’s moons. His design consists of the larger convex lens and a smaller concave eyepiece. Kepler later came along and used a convex eyepiece lens, which improves the quality of the image, but causes it to flip upside down. Sky viewing really depends on the amount of light you can gather, and the bigger the diameter of the large lens the better. The minimum size needed for good star watching is 8″, and Galileo-style scopes can’t reach that without getting really heavy really fast (at 8″ diameters, it’s best to replace the lens with a mirror, which Newton did with his design. The Newtonian scope is kit #11.)

The Gakken kit consists of a couple snap-together plastic end pieces to hold the lenses, some parts for mounting to a tripod or a 1 liter soda bottle, and 2 sheets of stiff construction paper to use for the body of the scope. With such a simple kit, you’d think it would be done in no-time. But, the paper doesn’t like being rolled up into a tight little tube, and when you add the glue to make the tube, it gets messy fast. Even pre-rolling the tube the night before and tying it up to pre-shape it was difficult because the paper wanted to crease. And then, the paper absorbs the moisture from the glue and gets all warped and soggy. So, it’s a real challenge to build this kit so that you end up with a nice looking end product. On top of which, it’s really hard to tell which directions to face the lenses because the curved sides aren’t noticeable. It’s a good thing that I pre-tested the lenses first, or I would have glued everything together with the big lens facing the wrong way.

But, in the end, I still wound up with another working kit. The viewed image is really tiny (about 1/16″), but still recognizable (the big lens is only 2″ dia.) It’s good for looking at houses a few blocks away, and at the moon. Plus the kit comes with 2 small lenses, one each for the Galileo and Kepler designs. Additionally, the mook has some nice galaxy photos, and it comes with a great poster that is actually intended to be part of the wallholder for the scope as a display piece. The finished scope is about 2.5 feet long, so it’s not as compact as something like the DC motor car. But, even though it didn’t come out looking all that great (stupid soggy paper that hardens like a rock) I’m still glad I got it. I learned more about scopes this way than when I’d bought my $400 Newtonian scope a few years ago.

Kt 19: Galilean Telescope

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