Planetariums...40 years apart.
categories:
- “art”
- “computers”
- “movies” tags:
- “stars”
Greetings gentle reader, hope you’re well and enjoying rich experiences. Last weekend I joined the fam at our local planetarium. I’m guessing it was a typical 60-footer maybe seated 100? Sloped floor, as is the fashion, overlapping LCD projectors with software to stitch the images together. It was neat-o.
But a few days later I realized that something’s lost in 40 years of technological improvement: black level.
In 1978, I was walking through the almost-opened addition to the Science Museum of Minnesota having ended my HS senior project in the exhibits department doing graphic arts tasks. I decided to go into the offices of the as-yet unfinished Omnitheater and asked if they needed p/t employees. I happened to talk to the right person who pointed me to the right person and I was starting as a console operator for $5/show.
An Omnimax theater is an Imax projector inside a dome. Revolutionarily for the time, the floor is sloped 23 degrees. The projector and film format are centered around a 30mm fisheye, the Hasselblad 30, with it’s central axis lowered about a half-inch off center. The projector version is substantially different mechanically since it doesn’t have moving elements or a diopter for exposure. Oh, and it has to withstand the heat of a 12,000 watt arc-lamp shining through it. That’s mostly accomplished by surrounding it with an enormous aluminum can and the film blocking most of the light. The lens can survive only about ½ minute of “raw” light through it. Running without film is to be avoided. Like the plague.
Now here’s the point: back in those days, Omnimax films were rare so it was thought that adding a planetarium would be a logical extension. Makes sense, except for that 23 degree slope. No conventional, earth-centric clockwork planetarium could handle that (at the time, though Minolta figured one out later. Nope, we needed one that didn’t mechanically link all the projectors so a non-level “horizon” wouldn’t freak it out.
We needed the Spitz Space Transit System. Don’t worry, we’re getting to black levels, actually faster than you think. The STS consisted of a 4’ starball, 5 separate planet projectors in a row behind it, and some zoomable projectors for the special stuff. Their names were evocative: Earth, Moon, and Sun. (There was room for 1 more, SMM didn’t buy it.) Off track: why only 5 planet projectors? Because at any one time at any point in space, you can only see 5. Space is big, very big.
Every projector in this selection featured something like this: an extremely high-precision light source. Usually a xenon arc-lamp the bulb of which was used to illuminate microscopes and as headlights on tanks. (They were highly precise and stupidly solidly built.) Then there was some kind of aperture (movable in Sun, Earth, and Moon), lenses, and finally a mirror that could pan and tilt. That’s it. Darken the room, put any of these up, and you have a nearly infinite, velvety black with a single point of light on it. Those mirrors were controlled by a Data General Nova 2 computer and it could move them around in ways that quickly fooled you into believing you were seeing 3d projection. Partly, due to the aforementioned velvety blackness and the sharp, tiny, bright point of white.
But the starball was different. It was a black aluminum sphere with protrusions that made it look like the most sci-fi sea-mine you could ever imagine. In fact, it would’ve made a perfect model for the Death Star. The smallest cylinders were little more that holes in the shell, with a tiny lens. (Smallest stars) The god progressively more complex until some of the towers were 6” tall with periscopic mirrors on top. In order to get all 10,000 stars in the right places, sizes, and colors, sometimes the light had to be bounced along the surface to get to ANOTHER post with a mirror that “threw” it to the dome. I’m telling you, it was the most magnificent thing you’ll ever see. Inside, each hemisphere had one of those durable arc lamps off near the “pole” that bounced the light out, towards the inner shell where a mirror bounced it back down to the dead center of the hemisphere. In the middle of a dozen miles of razor-blade foil that was blackened like guns are, coiled in a spiral, sat a hemispherical mirror that bounced the light out to all those openings, and out to the dome. The razor-blade coil was an ingenious solution to absorbing every stray photon from that xenon lamp. With the sharp-edges up, endlessly spiraling in towards the mirror, it made countless tiny valleys of black metal that absorbed the light or if it DID reflect, it did so in ever diminishing angles of the valley walls. It really worked too, the hemispherical mirror looked a drop of mercury on the blackest plate ever made. And like the planet projectors, this giant ball could roll, pitch, and yaw from the computer’s control.
Ok, ready? You’ve got an idea, infinite black space with 5 dots swirling around? Now let’s fade up the stars. 10,000 of them. Every star visible from earth’s orbit. Down to some ridiculous magnitude, “firefly butt at 100 miles” I don’t recall. Sure, a lot of the faintest ones—those stubby cylinders—were “fillers.” But holy moly, the first time you saw that thing, you had trouble breathing. Astronauts and astronomers would gasp and grin. Radiologists (who regularly use the most amazing monitors in the world) would do a double take. Photographers and cinematographers would quit their jobs. Just imagine the Milky Way, a zillion specks of light. Not one twinkle, either, every single point was sharp enough to go through the backs of your eyeballs. Majestically turning. Or, because we were teenagers, violently tumbling when we there wasn’t an audience. Absolute black, right next to absolute white. Each point, from a theater seat, literally infinite. Sure, up close, they were circles, but the audience never got to see that. Heck, even employees were smart enough to stay in their seats when it was “just stars” because the room was absolutely dark. No exit signs. We console operators even knew when these parts were coming up and would dim the console lights down to nearly nothing (if the computer was still running; if it was manual, then forget it, we needed 3 hands and a lot of practice.)
The STS was magnificent, but it was a one-trick pony. It was only ever just a planetarium. It was an electro-mechanical analog-digital display system three stories tall and costing north of a million bucks (1978 money folks). It was flaky as hell, in fact, it couldn’t actually DO a planetarium show when I started, the DG computer couldn’t run +2 planets and the starball at the same time. It would be my brother, hired as the night-shift technician for Spitz, who spent a year working on it, that finally got it working. I saw it exactly ONCE do “the real deal” showing a the inner planets in orbit around the sun as our imaginary spaceship slowly climbed out of the ecliptic. Ok, practically speaking, such a ship would’ve been traveling a HUGE % of the speed of light to see that view, and the noise of all those stepper motors was really loud. But it worked. My brother went on to write and run the Christmas star show with a University professor, but I was off to another Omnimax theater by then and never saw it.
Now, back to 2022, comfy seats, the usual mellow-colored cove-lighting starts to fade, our presenter introduces herself and her console operator, we get to a dimness that I thought was the last pre-show lighting…and up comes the stars. My eyes are 40 years older, I wear glasses full time now, and I’m moderately sure I could’ve walked out of a theater I’d only seen for less than a minute before the lights went down. The stars were…well, they had color (I couldn’t see it), and they could move any which way at any whim. But it was never dark. I think it got down to “rural Minnesota” dark. Not Antarctica or Sahara, or Mt. Everest dark, but something where, say, one street light might be within site (11 miles). Dark, certainly darker than any kid in that room had ever been in. But as I watched the stars and constellation figures move and fade in and out, I realized later it wasn’t earth-orbit dark. Reliable computers with powerful graphics cards and good software achieved something the Space Transit System could never do: they could show the stars, or Omnimax movies with equal ease. In fact, you could watch any movie you’d want on that dome: the software can present it such that all perpendicular lines will be square, stretching and distorting the image so the curve of the dome “undoes” that to make it look straight. You could even MOVE the movie’s window anywhere on the dome, that calculated distortion along with the perfect stitching algorithm making it look good anywhere inside the room. Or you could project a panorama from Mars in scale such that the audience is as close to the real thing as they’ll ever get.
But what it cannot do at all, not one little bit, is show you the truly infinite. To see the stars as only 12 men have seen it, in high orbit and lunar transit. The STS systems were a fucking nightmare of mechanical engineering, keeping them running was a job that still keeps me in awe of my brother. Just the number of anti-backlash gears—each needing clean and lube and careful tensioning—makes my motorcycle look like a single lego block. (And every axis of movement for every mirror had at leas 1 pair of those gears.)
Even from 40 years away, the sight of those stars is still burned into the back of my eyeballs.
