: surfing the web I came along Digistar's www site and saw that it uses , for
: projecting stars , constellations etc. a CRT , the light from which is
: projected on the dome through a fish-eye lens.
I recently had the chance to visit a Digistar-equipped star theatre
(Philadelphia) and was actually less than impressed with the quality of
the starfield that the projector rendered on the dome. The stars were
quite fuzzy and had an alarming tendency to jump about within their
constellations as the sky was in motion! Is this perhaps because Philly
has an early model of the projector or are new Digistars also prone to
The console operator didn't have much to say on this subject.
One thing which *was* spectacular about the Digistar, though, was its
ability to project animated computer diagrams over the entire dome. What
I wouldn't have given for that capability when I was in the business...
| $ |
|---. ,---. ,---. ,---. . ,---. ,---. ,---. | "Most people would sooner die
| | `---. ,---| | | | |---' | | `---. | than think; in fact, they do."
` ' `---' `---^ |---' ` `---' ` ' `---' | -- Bertrand Russell
| hsap...@clark.net |
> surfing the web I came along Digistar's www site and saw that it uses , for
> projecting stars, constellations etc. a CRT, the light from which is
> projected on the dome through a fish-eye lens.
> Since no planetarium using this modern technology is installed here in
> Greece, to check it out, I was wondering if anyone knows about the
> technology of such CRTs, since producing enough light for all these stars
> and effects on a 12 to 25 meter dome, requires a rather large amount of
> light, that normal CRTs have not the ability to produce (not even close).
Be happy that your country has no DigiStar planetarium.
A few years ago, the very first large planetarium in Sweden, "The
OmniTheatre", was opened in Stockholm. It uses the DigiStar
projector, and the image quality is NOT GOOD! The image is faint,
unsharp, and of course in black-and-white only. The DigiStar may
offer some flexibility, however the image quality is far inferior to
the image produced by a traditional Zeiss planetarium. I almost
never visit the OmniTheatre here in Stockholm, where I live --
instead I try to visit Zeiss planetaria in other cities of the world,
whenever I have the opportunity.
Paul Schlyter, Swedish Amateur Astronomer's Society (SAAF)
Nybrogatan 75 A, S-114 40 Stockholm, SWEDEN
e-mail: pau...@saaf.se p...@home.ausys.se
That's how both work. Now for the pros and cons.
1. Digistar images are monochromatic (a single color, light green)
Traditional projectors have proper star colors.
2. Digistar images are not as sharp as traditional, since it is a video
3. HOWEVER, only Digistar can show an audience the effect of proper motion,
traverse a sphere of the Earth's neighborhood in the Milky Way
approximately 900 light years in radius, bring up constellation pictures
for all 88, draw constellation boundaries, Right Accession and Declination
grids, celestial coordinates, and other effects that traditional
planetariums can not touch.
In my humble opinion, Digistar has a place as an excellent educational tool
for teaching astronomy. But you won't find me using Digistar only. I need
to see the real sky once and a while.
BY THE WAY.....traditional planetariums such as the Zeiss can run up to 2
million dollars (US), while a Digistar comes in at five to six hundred
thousand dollars (US).
I hope that you find this information enlightening.
Also, the London, England Planetarium just converted over to
Digistar...Digistar II that it. The NEW Digistar II uses a mini-tower Sun
workstation and has sharper stars and more memory.
Check it out!!!
John A. Schroer IV
Assistant Curator of Astronomy
Dayton Museum of Natural History
2600 DeWeese Parkway
Dayton, Ohio 45414
(513) 275-7431 ext. 36
>Traditional planetarium such as Zeiss and Minolta use >holes for the stars, and colored glass to give stars their >proper color. The light then passes through several
>lenses, and is projected onto the dome.
One other detail about the Zeiss, at least the Model VI we
have here in Boston, MA (Charles Hayden Planetarium):
The brightest stars (to mag. +1.0) each have dedicated
single-shot projectors mounted on the collars of each of the
large star spheres, outboard of the planet cages. This
allows for a much greater range of magnitudes than is
possible with a system that relies only on the size of the
holes punched in the star plates, or the intensity of the
CRT beam. This, IMHO, is what sets the realism of the Zeiss
sky apart from that of Digistar.
Of course, systems that use fiber-optic light guides offer
an even more tremendous brightness range combined with an
extremely small star image size on the dome. The realism
thereby produced is truly stunning.
Prior to the installation of our Zeiss in 1970, we had a
custom-built projector constructed by Bill and Frank Korkosz
(you may have heard of them) of Springfield, Massachusetts.
For a purely optical system it ranked among the finest (more
stars than even our Zeiss' 8900 stars, smaller images, and
even a Uranus planet projector!)
Charles Hayden Planetarium
Museum of Science, Boston
Unfortunately NO Planetarium projector is as good as the real sky.
That goes for contrast, color, and all visual elements. The debate about star
projectors has ranged for years and started long before Digistar. I
believe that it ignores a fundamental concept of the planetarium. We
have to ask ourselves what the facility is trying to do. We can't
outdo God, the Cosmic AC or whatever in reproducing the sky. The
Planetarium is merely a tool. If I'm trying to teach the
constellations or explain the motions of the Earth, explore the
mysteries of the planets, etc. - it all depends on how I use what
tools I have. I've seen people teach more astronomy in a portable
planetarium than in a huge theater with a Zeiss. That doesn't mean
the inflatable's sky is truer to the real thing. What it means is
that someone is doing a better job of teaching and that's a human
question not a machine question. And this is where our energy should
be spent. You can do it with a Zeiss, a Digistar, or any other
projector if you have the talent and the motivation.
The knowledge of the heavens for the average citizen is abysmal. The
knowledge of the average elementary or secondary school teacher when
it comes to astronomy is worse than ever and it affects what their
students know. These are our real problems today.
I do not mean that we should select flash over substance. But there
are real principles which computer graphics can demonstrate that a
fixed projector can't touch. Maybe we'll address them with Digistar
or video or laser projected via something like Omniscan. But they are
things worth teaching non the less. And what about all the great new
images and information provided by the Hubble Space Telescope or any
of the space probes of recent years. There's a whole body of
information in astronomy to teach and it doesn't depend what the stars
look like on a certain star projector.
If your thought is that the planetarium is merely a curiosity to be
visited once in a lifetime. And if you don't care about learning
anything - all you want is to "experience" a sky, then go find an old
projector in a big dome and stare at it. You'll be impressed.
But so what?
We need more people committed to reaching the people of this world
with the exciting discoveries and mysteries of astronomy. That
commitment - rather than worrying about star projectors and misguided
nostalga is what is important.
But then, I'm just a lowly planetarium person. I'll take what ever I
can get be it a Zeiss, a Digistar, a Spitz, a Goto, a Minolta, or an
Omniscan. Hey, wait maybe I should ask for one of each.
But none of them looks like the sky from the a real dark-sky site.
Guess what? It doesn't matter.
Jack Dunn - Mueller Planetarium-UNL
On the Web at http://www.4w.com/mueller
If you have a laser projector, join ILDA
Concerning the "Great Planetarium Debate," I'd like to offer one tiny
nugget of wisdom I've picked up after 20 years in the business and after
working for years with Digistar, two kinds of Zeiss projectors, a Spitz
A3P, a Starlab, and being familiar with other models and machines: there
is no perfect planetarium projector.
Every model has its strengths and weaknesses. One of the weaknesses of
Digistar is its (current) inability to project as crisp and sharp a
starfield as analog projectors and fiber-optics models. One of its
strengths is its ability to present honest-to-God three dimensional
astronomy as a part of its computer graphics capabilities which can educate
every bit as much as entertain. It looks different in different theaters:
on large domes with relatively low reflectivity, Digistar is dimmer and
fuzzier; on smaller domes with greater reflectivity, the images are
brighter and sharper. And Digistar's manufacturer continues to make
improvements--even as do the other planetarium manufacturers.
Any choice of planetarium projector requires compromise; those who buy and
use them must determine which strengths they wish to take advantage of and
which weaknesses they're willing to live with.
Different people come to different conclusions. And you know what? That's
Museum of the Rockies
Bozeman, Montana USA
* James G. Manning - Director | /\ MOR |
* Taylor Planetarium | / \ /\ |
* Museum of the Rockies | / / /\ |
* Bozeman, MT 59717 | / / / \ |
* am...@gemini.oscs.montana.edu |/____/__/____\|
That's exactly right! Planetariums ARE directed to those people. And
rightfully so. Who the hell wants to preach to the choir?!!
> Isn't this what planetariums really were meant to be used for: to
> learn your way around the sky?
Yes, and they still are...but not EVERY single show we present is about the
constellations. Planetariums have grown to be more than that - we present the
latest from the space program and the latest astronomical discoveries as well.
> Of course I know that most people
> aren't interested in this.
On the contrary, it is still the most popular topic under our domes.
Kevin Conod | kdc...@delphi.com
Dreyfuss Planetarium | Check out our Web Page:
Newark Museum, NJ | http://www.rutgers.edu/newark/MUSEUM/dreyfuss.html
>From am...@gemini.oscs.montana.edu Mon Jan 8 17:26:00 1996
>Any choice of planetarium projector requires compromise; those who buy and
>use them must determine which strengths they wish to take advantage of and
>which weaknesses they're willing to live with.
>Different people come to different conclusions. And you know what? That's
>Museum of the Rockies
>Bozeman, Montana USA
I've been waiting for this debate to resurface on this newsgroup... in my
opinion, this is more or less a variation on recent perennial debates such
as "Which is better: live or canned shows?" and "Which is better: large
or smaller theaters?"
A couple of others here have already raised this point, but I think it's
worth restating: "There's more than one way to be a planetarium." I've
had the fortune of working in several different theaters in several
different cities, with very different equipment and operating styles.
I've also been fortunate to see them all get the job done in their
Digistar is not, by any wild stretch of the imagination, a really good
simulation of the night sky. It is, on the other hand, a *really* good
educational tool, if it's users choose to employ it as such.
<soapbox mode off>
hey, but Zeiss is cool too.
ch...@laserfantasy.com Christopher A. "mothboy" Seale, signing off.
Performing live for Laser Fantasy at The Children's Museum of
Indianapolis..."There's a flame around here, I'm sure of it!"
>> Isn't this what planetariums really were meant to be used for: to
>> learn your way around the sky?
>Yes, and they still are...but not EVERY single show we present is about the
>constellations. Planetariums have grown to be more than that - we present the
>latest from the space program and the latest astronomical discoveries as well.
No one person can say "what planetariums really were meant to be used
for", since they can and are used for many purposes.
And I have to laugh at the notion of someone going to a laser show to see
Southern hemisphere stars! "But the dang laser keeps blocking the view..."
| Mark C. Petersen Loch Ness Productions 7225...@compuserve.com |
| ma...@lochness.com http://www.lochness.com mar...@scicom.alphacdc.com |
I don't generally get involved in this type of political
discussion, but in his response to this issue John A. Schroer
>BY THE WAY.....traditional planetariums such as the Zeiss can run up to 2
>million dollars (US), while a Digistar comes in at five to six hundred
>thousand dollars (US)
I take no issue with what John says, but wanted to add some
Optical/mechanical planetarium projectors have varying cost
depending on dome size. For a 60 foot dome the above prices
are probably quite accurate. But, at 50 feet price is
comparable, and at 40 feet and smaller, optical machines become
cheaper than Digistar.
The issue of cost hits a very sensitive nerve with me. When
our facility was designed, the only choices we had for a tilted
dome were a Spitz STS or the first Digistar. We went with
I can't speak to the costs of maintaining a Digistar II, but the very
first Digistar ever installed (here in Richmond, Virginia) is
QUITE expensive in my book.
Between new tubes (1/year), telephone support, and circuit
board swaps with Evans & Sutherland, we spend well over
$7000/year. That does not include E & S coming to our
facility, or the maintenance on our host
computer. (If we wanted to maintain the VAX, an annual
contract on it would be over $10,000.) This may be in line
with the costs charged for annual Zeiss service, but a
mechanical projector lasts a lot longer.
Everyone out there knows how fast technology is changing.
Through no fault of their own, E & S is finding it harder to
maintain our 12 year old system. We have been told that the
average length of support should be about 10 years. With that
as a benchmark, you would need to purchase 3 or 4 Digistars in
the life span of an average Zeiss, which makes the overall cost
Try going back to your funding sources every 10 years for
$600,000. We all know that it's easier to raise the initial
money before you open, than any additional money at a later
I often wonder why so many Digistars are sold. I have to think
it's a combination of the "gee whiz" technology and the price
tag for larger dome planetaria. But, if the decision makers
looked down the road 30 years, would they still make the same
>In article <4cu2cg$5...@agate.berkeley.edu>,
> <lhsa...@garnet.berkeley.edu> wrote:
>> Every model has its strengths and weaknesses. One of the weaknesses of
>> Digistar is its (current) inability to project as crisp and sharp a
>> starfield as analog projectors and fiber-optics models. One of its
>> strengths is its ability to present honest-to-God three dimensional
>> astronomy as a part of its computer graphics capabilities which can educate
>> every bit as much as entertain.
>How does that work?
>I suppose the Digistar cannot project holograms on the dome. What
>seems to remain is then using twin Digistar projectors, with either
>red+green filters, or polarizing filters + corresponding glasses on
>each person in the audience. But wouldn't that make the already quite
>dim Digistar image still dimmer?
the Digistar can present honest-to-God three dimensional *models* of just
about anything that can be represented with vector graphics (line
drawings, which can be fairly complex, but can't have "solid"
components). These models can be rotated on any axis at any speed, viewed
from any angle, moved to any three-dimensional position (in other words,
you can back away from them, move closer to them, or even move inside
them) and scaled any amount on each axis independently. All of this is
presented by a two-dimensional projection, but the ability to manipulate
such models is breathtaking when handled creatively (not to mention
addictive once you get good at doing it in real time).
hope this helps!
Yes, the Digistar is a different beast altogether from an opto-mechanical
star projector. In Cocoa, Mike Hutton considered the Digistar to be a
good special effects projector but a poor star projector. That is why he
installed both a Digistar and a Minolta Alpha Infinium. They compliment
each other wonderfully. By the way, Cocoa is an "open architecture"
planetarium. Should a better projector combination come along (and it
will), it can be installed in an afternoon. Of course, procuring funding
could take significantly longer....