|
|
Post by Ron Walker on Apr 19, 2022 19:45:37 GMT -7
Posted by: chemed Sep 17 2015, 04:02 PM
Hi Everyone,
Long time no "see".
My department recently acquired two StarLabs, the inflatable domes complete with star cylinders. So, of course, I offered to build a digital projection system for them. I have build a couple Dome Mirror setups for fixed domes. However, I'm wondering if a fisheye system would be a better option for a portable inflatable dome.
So I thought, what better place to get those opinions than OC? What do you think? For an inflatable, portable dome; dome mirror or fisheye?
-Adam
|
|
|
|
Post by Ron Walker on Apr 19, 2022 19:46:03 GMT -7
Posted by: moonmagic Sep 18 2015, 11:25 AM
Certainly NO expert here on portables, but that never stops me from forming an opinion....
I would GUESS that fish-eye in the center would be best due to footprint size and location. Most of the portables I have crawled in and out of had guests sitting on the floor, where they typically are seated near the dome edge. Seems projecting off of curved mirror might use up more room that smaller centralized projection source.
However, this depends on the actual equipment available for this project. You are always doing cool things. Rock on! mm
|
|
|
|
Post by Ron Walker on Apr 19, 2022 19:46:21 GMT -7
Posted by: Ron Walker Sep 18 2015, 11:25 AM
Not sure which would be best but I do have some observations. The fisheye again takes a position at the center of the room. Also I wonder about how much of the dome is actually covered. I would imagine that the spring line is not very high in the inflatable dome and the lenses must be fairly low to fill the dome. Also would the cone of light be blocked by any viewers not sitting directly against the dome. Also would this be a replacement for the StarLab projector or an adjunct for it. If the StarLab is used with it then having everything in the center of the room would probably be easier especially for setup
The great thing about the mirror dome is that it is out of the way and it projects the image flat across the dome at the horizon line. The big problem I have found is in the quality of the dome mirror itself and how well the picture stand up (but that would be the same for both types of projection). A front surface dome mirror would probably help immensely but their costs are considerable. From my own experience I find that while there is certainly a "wow" factor with the dome mirror projection, I am not terribly happy with the image result. How much better a front surfaced mirror would help I don't know but the system, for me at least, would still be limited by BluRay resolution. A dome is a lot of area to cover with a picture.
What have you used and what is your opinion of the image quality for the systems you have built already?
|
|
|
|
Post by Ron Walker on Apr 19, 2022 19:46:45 GMT -7
Posted by: chemed Sep 18 2015, 01:35 PM I can see the benefits of both. I think the smaller footprint of the fisheye lens system would be good for the portable dome and would also be conducive to the portability of the system. It could also be slightly raised on a stand to raise the springline above that of the students' heads. I would follow something similar to the LSS system. www.lss-planetariums.info/index.php?lang=en&menu=projector&page=projectorAnother nice thing about fisheye systems is that there is software available that can output in a 360 (er...180) format. Both World Wide Telescope and Stellarium have a setting that allows for fisheye projection. You can also project fisheye video on these systems without having to purchase warping software as is the case with mirror-dome setups. Ron, I have had great success building dome/mirror systems that produce amazing quality images. The last one I built used an Optoma TX 1080 projector and a front-surfaced mirror from Acril Convex. I also used a double mirror system do reduce the amount of space. paulbourke.net/exhibition/domeinstall/adam2.jpgI posted somewhere in this forum about where I sourced the other (flat) mirror. I remember them being pretty cheap although I'm not really sure where it's buried. Digitalis also makes a "portable" version of this setup paulbourke.net/exhibition/domeinstall/newtonian2.jpgI found that 1080p resolution in a 24ft dome was more than adequate as the entire dome surface doesn't get used. I definitely learned that the devil is in the details. A front-surfaced mirror makes a huge difference. I also found that a projector that is capable of projecting brightly (high lumens) and a high contrast ratio (above 2000:1) is also important. I think Paul Bourke has said that the contrast ratio of the projector is more important than lumens. After that, some time needs to be spent on the orientation of the mirrors relative to the projector and the dome. A ""few" tweaks to get it just right can be a process but, once it's dialed in, it looks great. I also used a piece of software called meshmapper to make the dome images work properly for the set up that I used. -Adam |
|
|
|
Post by Ron Walker on Apr 19, 2022 19:47:03 GMT -7
Posted by: Ken Miller Sep 18 2015, 06:14 PM
I can usually be counted on to sing the praises of fisheye projection, but I think mirror projection would be fine. Inflatable dome systems are sold in both flavors, and the manufacturers eagerly extol the virtues of their particular system. I would stick with what I had experience with; in this case it would be mirror projection. There are hassles with setting up fisheye systems, and a learning cure to overcome, just as is the case with mirror setup. I can do fisheye projection more cheaply, but I don't think that is necessarily true for everybody.
|
|
