The Planetarium’s Beginnings

Mac Gardiner:

The planetarium first appeared in a list of the programs that the BPAA had in mind for the Observatory. John Rudolph was its principal proponent, based on its wonderful opto-mechanical structure, and also the fact that he was intrigued at designing the projection ceiling.
He designed and built the first prototype star field projector, using a miniature high intensity light source. It produced spots on the ceiling that you could only see in total darkness after 20 minutes of eye adaptation. He had no answer for the projection of most of the celestial objects people want to see, such as moon, planets, comets and asteroids.
The projection screen would have dominated the conference room, so he designed a series of collapsible screens, along the lines of a baby carriage hood. They ended up on ‘permanent hold’, as we found that Paul Below’s use of Starry Night software and a computer projector was highly effective in introducing beginners to the celestial phenomena.
As I detailed in an article in the January -February 2005 issue of this newsletter, BPAA rose to the challenge of developing a better projector. Many folks, including Allan Saunders, George McCullough, and Bob Matthews, worked on the problem. The lens designer Matthew D Watson gave us a plan for a 10-element lens that was good to 165 degrees. We estimated that the glass purchase alone might amount to $15,000 and the design and construction of the mechanical elements might raise the total cost to about $35,000.
I found an add-on camera lens that would extend the Boxlite projection field to about 115 degrees and demonstrated it to the BPAA board as an example of what might be obtained with the “Watson” lens. At the demonstration, Cathy Koehler handed me a clipping about a planetarium projector built in East Bremerton. The projector price, at that time, was $10,000. The system was complete, and used free, open source software. The closest competitor cost about $250,000 and had fewer capabilities. There was no doubt about it… it was a solution. The only weak element was the name “Digitalis.”
The rest of the story of BPAA Planetarium development, dome design, is covered by Jim Vaughan, except for this postscript—
The following March, I visited the Griffith Satellite Observatory near LA. It featured a planetarium. I learned that they had carried out a nearly parallel development. They also, with some trepidation used an elliptical, rather than hemispherical, dome, and found it fully satisfactory. They worked with the developers of Starry Night to produce a new program, Starry Night Dome, for Planetarium use. The last point is ironical:
They happened to run across a firm, Elumens, that produced hemispherical projectors for game simulators ( 6’ dome) in Redmond Washington. Elumens produced projectors with either a 165 Degree or 180 degree field of projection! They had to make the trade-off we know so well; either have a low stand with the 165 degree, which would bother viewers in the near rows… or a massive tower to support the 180 degree at five foot clearance (clears all seated viewers) They could use the high stand as the system was planned for a permanent installation. They were fascinated to learn about Digitalis, and agreed that a portable installation could reach the larger number of viewers available, on site, at schools. They figured “ student outreach” to be the principal objective.

The outside of the BPAA meeting room Planetarium dome. Photo by Bill O’Neill

The outside of the BPAA meeting room Planetarium dome. Photo by Bill O’Neill