New Member - Many Questions, "pinhole lens" light source - wish list and call for help
Nov 25 2008, 10:27 AM
Joined: 20-November 08
From: Iowa City, Iowa, USA
Dear Ron and Owen,
Thank you much for your thoughts on this topic. I really appreciate the photos. What's nice to see is that individuals and manufactureres come up with a variety of solutions... sort of a fun thing to see, as it is "anti-mass-production" and demonstrates individual ingenuity.
Alas, it looks like while there is a Nova III on ebay, the seller want's $500 (so far). I'm on such a steep part of my "upgrade curve" that that seems too much for me right now (for example, I covet a 10" diameter worm gear so that I can cut into a 1/4 (90 degree) pie shape and use it as a latitude adjustment gear (my projector is not and won't ever be "dynamically balanced", so I need a big gear and the worm design offers much tooth-contact area, etc.).
Ron, I coulnd't agree more about the blase nature of video projected star fields. I just love the magic of the electro-mechanical tecnhology and even suspect that it is PART OF THE DRAW for kids, when they see this weird, almost scary apparartion of "stuff" in the center of the theatre! I still recall first seeing the Goto "Saturn" model down in St. Louis and marveling at its construction. I say more of that stuff and less computer simulations!
Wow, the bulb issue is considerable, as I imagine it should be. If anyone has a sample bulb I could try, I'd be appreciatitve. I'm currently playing with the little ones that terminate in bare wire leads (I don't have a "stinger" per se, but rather one that has a similar form factor - its a ray-o-vac 3.6V, 0.3 model). That sort of bulb can "plug" into the I.C. type socket pins (i.e., 0.1 c-c spacing). I hope that I'm not designing myself into corner by leaning toward this sort of lamp socket.
One trick (for me at least), in designing the weighted-and-gymbaled horizon cut-off mechanism was the old problem with slip-rings (or in my case, lack of them)... to account for diurnal rotation of the bulb/starball and the wire-twisting implied. Here's my tentative solution: to use old-fashioned 1/4 inch "in-line" phone jacks (mating male and female ones). They have mechanical rigidity and -- if you go for the "mono" phono plugs rather than the 3-contact stereo plugs, the torsional force (resistance to twisting) isn't too bad. I would have likked to use a stereo phone jack, to provide for a "back up" circuit in the event of bulb burn-out. But one does get more resistance to slipping. So, I'm going to try to use the two mated phone plugs as part of the "stem" that orginates out of the south pole. I hope it works.
From the above discussion, it seems that the whole issue of realistic planet motion is a bear. Darn it! But that's down the line for me anyway. Gotta work on improvements to the diurnal and lattitude mounts, this horizon cut-off mechanism, continued mounting of lenses, and trying somehow to talk my wife into the "value" of buying a worm gear that just doesn't quite work for our budget. It sure would help me if I could find a home for this projector -- I'm trying, but am not very well connected to the "right people" in my area of iowa city.
thanks again for your interesting input.
Iowa City, IA
Iowa Space Science Center project
Other Projects: Science education, Spitz A4, Home-built planetarium
(6.35 limiting mag); single fisheye digital projection system. Spitz 373,
and the Spitz Jr.!
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