Portable Planetariums Have Closed the Gap

2025-08-26 / Karrie Berglund / Portable Planetarium

About fifteen years ago, I received an email I will never forget: a potential customer was looking to upgrade their fixed-location planetarium to a digital system. The writer was under the mistaken assumption that Digitalis only sold portable digital planetariums. Their email read, “We wanted to buy a real planetarium, but we couldn’t afford one, so we’re contacting you.”

This idea that portable planetariums aren’t “real” planetariums frustrated me then, and it persists today despite vast technological changes in mobile planetariums. While there are many differences in the two dome environments, our fixed and portable systems can offer the exact same software functionality and usability.

What was once a substantial gulf between portable planetariums and fixed-location planetariums has essentially disappeared, but the idea that portable planetarium systems are somehow lesser than their fixed counterparts remains.

What is a Portable Planetarium Anyway?

As the name suggests, portable planetariums are designed to be easily transported and set up in a variety of locations. They're commonly used for outreach programs by science centers, children’s museums, and colleges/universities. Rather than busing students to a planetarium facility, school districts often invest in a portable planetarium that they can bring to the students, saving time and giving teachers more flexibility with instruction.

A typical portable planetarium consists of a projection system, inflatable fabric dome, and blower to keep the dome inflated. Audiences in portable domes usually sit on the floor, which limits comfort but enhances portability and simplicity. Portable planetariums are significantly lower cost than fixed-location planetariums. We put a lot of extra care into making sure these systems are rugged, reliable, and easy to use.

The Basics of Fixed Planetariums

Fixed planetariums, by contrast, usually feature rigid domes made from materials like perforated aluminum or fiberglass. These are permanently installed in a building, eliminating the need for an inflation fan. Fixed projection systems can be digital or analog (starballs). Most fixed dome systems sold today are digital because they are far more flexible.

Fixed domes tend to offer a more luxurious environment:

• Built-in seats and full height doors make fixed domes more suitable for older audiences or those with restricted mobility.
• Can be higher resolution and brighter if multiple projectors are used
• Surround sound is common
• Cove lighting for ambient or special effects

Fixed domes also bring unique challenges: high cost to build; requirement of dedicated space; precision projector alignment if more than one; and maintenance complexity.

Portable and Fixed Planetariums of the 1970s

The first commercially available portable planetarium launched in 1977. This was the analog StarLab, which featured a central gimbal-mounted light, two side lights, and interchangeable film cylinders that slid over the projector lamp to display different imagery. There were cylinders available not only for starfields but also for constellations of various cultures, bird migration routes, the biological cell, and more.

With the StarLab projector, it was possible (though time-consuming) to roughly position the major planets and the moon along the ecliptic in the starfield cylinders. Each planet magnet had a small mirror that could be angled to help fine-tune its position.

The StarLab cylinder system had some major limitations. You had to change cylinders if you wanted to show both the northern hemisphere sky and the southern. It was not possible to demonstrate planetary or lunar motion accurately. The original StarLab was truly a star projector rather than a planetarium.

By contrast, starballs in fixed domes from the late 1970s offered more sophisticated capabilities. They simulated annual motion, highlighting the movement of the planets against the stars. They displayed moon phases, and some starballs even demonstrated precession of the equinoxes. They could project the sky from any point on Earth, with no need to change equipment to display the opposite hemisphere.

1970s starballs still had limitations compared to today’s planetarium systems. They too were restricted to Earth-based perspectives, and their constellation display capabilities were typically limited to just a few major constellations or the use of individual constellation projectors installed around the perimeter of the dome. However, they offered far more advanced capabilities than 1970s portable planetariums.

Modern Fixed Planetarium Systems vs. Portable Systems

Computer-based planetariums for fixed domes have existed as far back as the early 1980s. However, they only started selling in large numbers in the late 1990s and early 2000s. I estimate that today there are well over 3,000 digital planetariums around the world, in portable and fixed domes.

As noted above, Digitalis sells digital planetarium systems for both portable and fixed domes that run the exact same software and feature the same user interfaces. You can develop content that works equally well in both dome types. Why is the system in a fixed dome a “real” planetarium while a system in a portable dome is not?

There are of course still differences between portable and fixed planetariums, but most relate to the dome setting itself rather than functionality. Even among fixed planetariums, there can be a large variety of environmental differences that are completely independent of the system itself.

Similarly, how portable planetariums are used also varies. Some inflatable domes do use certain types of portable seating or surround sound systems, for example, but this comes at the cost of capacity and/or increased setup time.

Conclusion

Although some biases remain, the gap between fixed and portable systems has all but vanished. Portable planetariums now offer incredible educational experiences just like their fixed counterparts — and, unlike a fixed dome, they can take the stars directly to the students.