Otona no Kagaku Kit #39 Review

(Image taken from the Otona no Kagaku site for review purposes only.)

Otona no Kagaku Kit #39, the Updated Pinhole Planetarium. 3,500 Yen ($35 USD), Released 07/25/13.

Kit #39 is pretty much like the original kit, #9. So, if you have the first one, is there really a need to get the second? Probably not. But, if you don’t have a planetarium right now, #39 is worth getting. Improvements include a more detailed star map, the options for picking the northern or southern hemispheres, a smaller lamp bulb that puts the projected starfield into higher focus, a motor mechanism that rotates the planetarium once every 15 minutes, and an auto-off circuit so you can fall asleep with the lamp on and still not run through batteries really fast. This kit is also a little easier to build because the dome sheets aren’t so stiff and brittle.

(Full kit, right out of the box.)

In essence, a planetarium is just a set of photographic plates with a light source, for projecting images of the night sky onto the walls of the room, or a screen of some kind. The more elaborate systems contain multiple lenses, motor control, and the option of selecting parts of the sky to project. The only real science here involves pin holes, the ratio of the illumination filament length to the pin hole size, and distance from source to pin hole to projection screen. To get the right kind of lamp, Gakken went to a small shop and commissioned the production of custom-built bulbs specifically for this kit (which arguably is a problem when you need to buy a replacement).

(Assembled motorized base. A thumb screw at the hinge point lets you adjust the dome angle to simulate the view of the sky from your latitude more realistically.)

The kit is assembled in two parts – the motorized base, and the dome. The base is pretty straightforward, except when it comes time to screw the circuit board in place. The battery wires are short, and there’s a push button switch at one corner of the painted-side of the board. Also, one corner of the base has a triangular part that acts as the on-off switch piece. You need to orient the board so that the switch is under the triangular on-off piece. It’s pretty obvious if you try to match up the base and the circuit board before plugging the wire connectors in place. The wiring jacks have “Battery”, “Motor” and “Lamp” stenciled in English, which helps a lot. (The lamp wires are yellow and blue. The motor wires and battery are both red and black, but the connectors are different shapes. When you plug in the motor, make sure the red wire aligns with the “+” of the connector. Be careful, because when you put the circuit board in place in the base, you can’t see the stenciling.)

(Fully assembled dome, with the base plate facing to the left.)

The dome is made up of 5 of the 6 supplied sheets. You get the northern hemisphere if you use sheet 1, and the southern hemisphere with sheet 4. One side of each sheet will look duller than the other – it has a thin protective layer that you peel off at the end of construction, and represents the outer surface of the dome. For the sheets with 3 panels, pre-crease the panel fold lines away from the dull side. Then, pre-crease the tab fold lines toward the dull side. It also helps to pre-plan how you’re going to attach the sheets to each other, so that the “A” tab on one sheet aligns with “A” on the other; “B” with “B”; and so on. Put the double-sided tape near the fold line on the tab (you’re going to trim the tab excess with a scissors, and you’ll want as much tape holding the tabs together as you can get). Put tape on all the tabs at one time, this will make assembling the dome easier later. Make sure you leave the paper on the tape, with one end partly removed and folded over, then pull the paper off carefully one tab at a time as you address each panel individually. When the dome is fully assembled, look at the plastic base support. There’s a really small notch on the edge of the collar cylinder piece. Make sure that notch aligns with the tab labeled “4” on the dome. Finish the dome by putting the black “V” tape pieces at the edges of all the tabs to seal the corners to prevent light from leaking out, and trim the tabs to a length of 4-5 mm with a scissors. The notch on the dome base collar aligns with a small triangle arrow on the motor assembly column.

Suggested assembly time is 90 minutes, and it took me closer to 2 and a half hours because of all the taping. You’ll need a small Phillips screwdriver and scissors for assembly. The kit uses 2 C-cell batteries. The power switch has three settings: Lamp Only; Lamp and Motor; Off.

(With the dome mounted on the motorized base. Reminds me of a dog with a funnel collar around its neck. The actual planetarium looks much better than the picture.)

The mook cover features singer/actress/fashion designer Tomoe Shinohara in the Planetarium Bar in Ginza. The first article is a photo gallery of astronomy pictures from various photographers. This is followed by an interview between Tomoe and planetarium designer Takayuki Ohira (of Megastar Corp.) There’s 10 pages on the design and manufacture of the bulb used in the kit, with photos of the different manufacturing steps. We then get more star photos, and instructions on how to prepare for an evening of star gazing, apparently sponsored by Vixen Optics, a manufacturer of telescopes and binoculars. There’s 10 pages on an amateur rocketry club and the successful launch of their low-cost, 250-pound rocket. One other article is entitled “4 Puzzles About the Constellations” (one of which is how the main stars in Perseus have been moving apart from each other over the last 2,000+ years, so what we see is different from what the Greeks saw).

(Underside of the base. The plug connected to the right side of the circuit board is for the motor. Note that if you reverse the wires to the circuit board, the globe will rotate backwards. The mook doesn’t say anything about what the S2 pads are for.)

Suggested kit mods include making a light-sensitive “theremin” harp to accompany the star projections; adding a small slide projector to show the moon along with the star map; and creating a tent from an umbrella and hanging the planetarium kit inside as a personal IMAX theater. The one article on hobby projects is on a guy hand-making his own tank. A new section consists of 5 astronomy puzzles (like locating the big dipper from the kit’s star map and finding certain constellations at certain times of the year). Finally, we get another of Yoshitoo Asari’s Science Manga chapters, this one on how astronomers can tell what the Milky Way looks like, given that we’re sitting inside it.

The kit’s lamp isn’t all that bright, so you have to be in a pretty dark space, or wait until the sun goes down, to be able to see the projections on the walls of a room. But it is really pretty, and the motor lets you see the constellations rising and falling, if you want. It is a fun kit to build and it’s great for anyone wanting to start out as a star gazer. The pictures in the mook aren’t as interesting this time, but I do like Asari’s manga, so that’s a plus.

Next up:

Kit #40, the miniature special effects camera. This is going to be a webcam with a special lens designed for filming your own miniature movie sets. Expected out in September, 2013. No suggested price.


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