Stars under the microscope

Franco Dittert needs good eyes and steady hands when he threads glass fibers thinner than a human hair for the starry sky in planetariums.

He places up to 300 stars on a disk the size of a 20-cent coin. It needs just 32 of them to display the entire starry sky: Franco Dittert works as a star threader. He makes sure that planetariums can project stars into their domes with pinpoint accuracy.

That sounds like a romantic job. Who wouldn‘t want to work in the firmament? Dittert is still fascinated by this time and time again. But he is not interested in romanticism. “That might have been nice around 20 years ago if I could have explained the starry sky to my wife as well as I can today,“ he admits. Today, he is fascinated by the delicate technology that makes the stars twinkle in planetariums around the world.

He played a key role in this. He threads hair-thin glass fibers, just 85 micrometers thick, into tiny holesthe latest generation of ZEISS ASTERION star projectors. Each one subsequently becomes a star in a planetarium dome. It has to be perfectly positioned so that the stars shine in the right place in the projection on domes of up to 18 meters in diameter.

The Bavarian has been used to precision work for accurate illustrations since his training. He trained as an optician in Rosenheim. In his previous job, he mainly worked with eyeglass lenses and contact lenses to create sharp images on customers‘ retinas. Today, by contrast, he produces the miniaturized star projectors that generate sharp images in a planetarium dome.

Dittert found out about star threading at an orientation event in Oberkochen when he accepted a position in the 3D laser technology department. At that time, he visited the smallest planetarium in the world. This fascinated him so much that he immediately applied for a star threading position based in Jena when it was advertised in 2020. He was even prepared to move to Thuringia with his entire family for it.

Now he is threading stars under the microscope. Analog star projectors, digital projectors and intelligent software all create the overall display in the planetarium. Dittert is confident about the particular advantages of his precision work for the analog world, „Our analog work allows high-resolution, brilliant stars to be projected. Digital technology can‘t do that.“