I have recently come across what I would describe as the best low-cost (around 4 dollars) pinhole star projector that I have seen to date—a Kenko Star Roman star projector.

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The Kenko Star Roman star projector

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Its design is similar to any typical pinhole star projector: a base (left) that holds the light source and the batteries, an acetate (right) with constellation patterns, and a transparent protective cover (top).

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Light source of the star projector

The projector was originally fitted with an incandescent bulb. Since an incandescent bulb does not usually perform well as a light source for pinhole projectors (since it uses a filament that is not exactly round and ‘point source’), I have decided to replace the bulb with an LED, in particular, one with a very small light-emitting material. If you use a typical LED with a large light-emitting material, it will perform no better than an incandescent bulb. It may take some experimentation to find an LED that will work well, but in this DIY project, I have found a suitable replacement from an Eveready flashlight.

The smaller and brighter the light source is, the sharper and brighter the projected images of the stars (perhaps a laser diode will perform much better than a flashlight LED, but that will be for another DIY project).

Shown below is the acetate with printed star patterns. Labels of constellations are written in Japanese.

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The projector’s acetate with constellation patterns.

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When you hold the acetate against a white wall, you can actually see the transparent portion (the star patterns).

This projector only shows the stars of the Northern Hemisphere.

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Two size D batteries power the projector

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Some usage suggestions printed on the side of its box.

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Constellations projected on the walls and ceiling of a room using a Kenko Star Roman star projector. It works in the same principle as a DIY flashlight star projector. For a larger image, click here.

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For DIY astronomy projects useful for astrophotography, click here.
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© Anthony Urbano (Manila, Philippines)

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