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Post by Ron Walker on Jun 13, 2022 14:12:39 GMT -7
Posted by: Ron Walker Sep 9 2017, 03:08 PM The projected stars look nice and round. How big in diameter are then and how far is the projection? I'm sure you said someplace but I'm old. huh.gif
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Post by Ron Walker on Jun 13, 2022 14:13:06 GMT -7
Posted by: Philostopher1 Sep 9 2017, 07:25 PM QUOTE(Ron Walker @ Sep 9 2017, 03:08 PM) * The projected stars look nice and round. How big in diameter are then and how far is the projection? I'm sure you said someplace but I'm old. huh.gif
The largest star is about 1\4" at 5- feet away. The pinhole projecting it is about 2mm. I punched these with a pushpin and sanded the aluminum from a pie tin. This technique makes very good pinholes. Eventually, I'll compare drilling and sanding on thin aluminum ( we have lots of Sarah Lee pie tins around) to etching the holes against a laser ablated photo resist mask. Probably by a simple saltwater etching process. This does work great as there is lots of precision possible but it is an art in itself. I suspect clamping and drilling sheets of aluminum, then running an orbital sander over them to deburr, then cut and mount each individual star... I am already questioning my own sanity...
Regarding the current star projection, I didn't pay much attention to my led lens set up in all of the previous pictures. I just glued parts together with LED under the fisheye not paying attention to focal length. That fish eye has about a 4mm fl for smartphone sensors. I had the led a good 10mm behind it. By remounting the lens today at the proper focal length, the emitter appears to be about 1 mm diameter looking back through the lens! The Spitz arc lamp in the 512+ series was 0.8mm (if I recall) .Previously, with the lens being farther back, the led appeared significantly larger. When it's dark tonight I'll test and see if there is improvement. I expect some!
As far as age, I am 52. When I was in India I got very sick. TB was part of it. Since then I have memory problems and other issues due to a small lesion in my right temporal lobe. Fortunately my last MRI indicates it is shrinking. Such is being human. We can only do our best with what we have (or have left) to work with.
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Post by Ron Walker on Jun 13, 2022 14:13:23 GMT -7
Posted by: Ron Walker Sep 10 2017, 11:28 AM Once you get to two mm pin holes you will probably want to use a lens so the stars don't project too big. How big a dome are you going for?
We are all insane to be doing this in the first place but it keeps us off the streets as they say. Unfortunately you must wait another ten years before you can be called eccentric but your working toward that goal very well. blink.gif
I believe you will do well drilling each star in your star hemispheres directly. Only several thousand holes to go.
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Post by Ron Walker on Jun 13, 2022 14:13:42 GMT -7
Posted by: charles jones Sep 10 2017, 12:40 PM I am looking forward to your results with the mirrored ball at the center. I pondered this arrangement for some time. For me it seemed too big a task to take on. But, agreed, it does put the light source about twice as far away from the pinholes which is a distant advantage. And remember, you may not need a complicated artificial horizon cutoff like the Model B. Perhaps it is just a black cloth skirt around the entire projector. Jamie, the main thing is to get the brightest light source (LED) you can find, because there will be a loss of light. You might, in the mean time, experiment with a silver Christmas ornament.
One thing I found is that the ball should be as small as practical. If you experiment, you will notice that viewing the projected light source in the mirror ball, that image shifts as you view it towards the "equator" of the star globe. The smaller the bulb, the smaller the shift. So in reality, you wouldn't want to really use a Christmas ornament for the actual projector.
I don't know of any company that would "front surface silver" on a ball. Obviously it can be done, I am not sure how. The ball doesn't have to be silvered all the way around. You can easily calculate how much of it has to be silvered.
You might research and see if anything like this is already available.
And, while I think of it, Ron I am losing it. You are right, in the Model B, the lamp is not over Polaris, but indeed Polaris is 23 1/2 degrees away from the lamp. I guess the lamp is mounted at the "ecliptic pole" (if that is the name for it).
In any event, if Jamie goes for this arrangement, I am eager to hear the results. Everything is a challenge.
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Post by Ron Walker on Jun 13, 2022 14:14:03 GMT -7
Posted by: Ron Walker Sep 10 2017, 01:48 PM QUOTE(charles jones @ Sep 10 2017, 12:40 PM) * I am looking forward to your results with the mirrored ball at the center. I pondered this arrangement for some time. For me it seemed too big a task to take on. But, agreed, it does put the light source about twice as far away from the pinholes which is a distant advantage. And remember, you may not need a complicated artificial horizon cutoff like the Model B. Perhaps it is just a black cloth skirt around the entire projector. Jamie, the main thing is to get the brightest light source (LED) you can find, because there will be a loss of light. You might, in the mean time, experiment with a silver Christmas ornament.
One thing I found is that the ball should be as small as practical. If you experiment, you will notice that viewing the projected light source in the mirror ball, that image shifts as you view it towards the "equator" of the star globe. The smaller the bulb, the smaller the shift. So in reality, you wouldn't want to really use a Christmas ornament for the actual projector.
I don't know of any company that would "front surface silver" on a ball. Obviously it can be done, I am not sure how. The ball doesn't have to be silvered all the way around. You can easily calculate how much of it has to be silvered.
You might research and see if anything like this is already available.
And, while I think of it, Ron I am losing it. You are right, in the Model B, the lamp is not over Polaris, but indeed Polaris is 23 1/2 degrees away from the lamp. I guess the lamp is mounted at the "ecliptic pole" (if that is the name for it).
In any event, if Jamie goes for this arrangement, I am eager to hear the results. Everything is a challenge.
Charles
Well....I wasn't going to say anything..... unsure.gif
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Post by Ron Walker on Jun 13, 2022 14:14:21 GMT -7
Posted by: mrgare5050 Sep 10 2017, 02:23 PM youtu.be/B0o9IQbbVGQthis video from Mr Philostopher1 is utterly priceless, where has this been hiding - you are looking, if you are conscious ... its full of hilarious quotes ... inside this strange domed structure of weird shadows - fabulous description when Adler was new. THIS is the attitude the astronomers attain this end, and the tourists THINK they do, so everyone is happy these queer mechanical gyrations that looks suspiciously like the North America nebula in their picture of the sky, but the tourists wont care ha!
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Post by Ron Walker on Jun 13, 2022 14:14:46 GMT -7
Posted by: Philostopher1 Sep 11 2017, 09:41 PM QUOTE(Ron Walker @ Sep 10 2017, 01:48 PM) * Well....I wasn't going to say anything..... unsure.gif
Yesterday I spent 10 hours painstakingly measuring my lens led arrangement to determine precisely how my lens is distributing light. "Mozeat" claims it is a 238 degree lens. Reality says 190 degrees +\- The arrangements works well and allows enough offset up or down to cover any gap created by the yoke. HOWEVER the stars become very eliptical around 170 degrees. I don't think I can live with that. So onto the Spitz approach...
Since I last posted, I inquired, with Thor Labs, Edmund, Newport etc. to coat a 10mm ball. EXPENSIVE!!!
Charles or Ron, anyone know the size of ball Spitz used? I am not sure if I assume a given size in the patent drawing if that would be anywhere near accurate...
I am trying to figure out the optics to collimate the LED and focus it on the ball right now.
Thanks for the input. Many heads are better than one on this.
I just got this as a gift today!
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Post by Ron Walker on Jun 13, 2022 14:15:03 GMT -7
Posted by: Ron Walker Sep 12 2017, 11:54 AM QUOTE(Philostopher1 @ Sep 11 2017, 09:41 PM) * Yesterday I spent 10 hours painstakingly measuring my lens led arrangement to determine precisely how my lens is distributing light. "Mozeat" claims it is a 238 degree lens. Reality says 190 degrees +\- The arrangements works well and allows enough offset up or down to cover any gap created by the yoke. HOWEVER the stars become very eliptical around 170 degrees. I don't think I can live with that. So onto the Spitz approach...
Since I last posted, I inquired, with Thor Labs, Edmund, Newport etc. to coat a 10mm ball. EXPENSIVE!!!
Charles or Ron, anyone know the size of ball Spitz used? I am not sure if I assume a given size in the patent drawing if that would be anywhere near accurate...
I am trying to figure out the optics to collimate the LED and focus it on the ball right now.
Thanks for the input. Many heads are better than one on this.
I just got this as a gift today!
At my age that book would give me a headache.
I've looked inside some of these projectors and the ball appears to be about two inches in diameter. I can't see why this ball would need to be any exact size but then I'm not an optician. You might want to experiment with a silver Christmas tree ornament. They are made out of extremely thin glass so the reflection off of the glass surface might not project double. I've looked at reflections in ornaments from about one to four inches in diameter and they all appear to work the same. Anyway worth the experiment. If things look good then spray painting the outside with silver paint might work as well.
As to collimating the LED light I see no reason for it. You might want to use the type of wide angle lens that Spitz started using with the A4 and the 20 watt arc limp to get the size of the light source down even more.I can see a small diameter tube with black flocking in it to absorb any light from straying outside the diameter of the small silver ball mirror. When picking collimating lenses for the brightest stars get a plano/convex lens with a focal length equal to the distance from the star hole to the mirror ball plus the distance to the light source.
All of this is just me thinking out loud and may not work at all so don't confine yourself to my rantings.
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Post by Ron Walker on Jun 13, 2022 14:15:23 GMT -7
Posted by: Philostopher1 Sep 12 2017, 09:28 PM QUOTE(Ron Walker @ Sep 12 2017, 11:54 AM) * At my age that book would give me a headache.
I've looked inside some of these projectors and the ball appears to be about two inches in diameter. I can't see why this ball would need to be any exact size but then I'm not an optician. You might want to experiment with a silver Christmas tree ornament. They are made out of extremely thin glass so the reflection off of the glass surface might not project double. I've looked at reflections in ornaments from about one to four inches in diameter and they all appear to work the same. Anyway worth the experiment. If things look good then spray painting the outside with silver paint might work as well.
As to collimating the LED light I see no reason for it. You might want to use the type of wide angle lens that Spitz started using with the A4 and the 20 watt arc limp to get the size of the light source down even more.I can see a small diameter tube with black flocking in it to absorb any light from straying outside the diameter of the small silver ball mirror. When picking collimating lenses for the brightest stars get a plano/convex lens with a focal length equal to the distance from the star hole to the mirror ball plus the distance to the light source.
All of this is just me thinking out loud and may not work at all so don't confine yourself to my rantings.
On the Photonics field guide book. I have to have my tablet next to me and google handy to even understand 1% of what is in that book. It is nice though as it is straight to the point. This project is testing my intellectual capabilities to the redline. I feel like my head is going to explode.
Wow 2inches! Hmm. I have seen smaller glass silver ornaments. My concern with collimating comes from gathering the light into one area as much as possible. But as I ponder this I think a lens may effect divergence through the pinhole and worsen it. Also, considering that a reflector telescope gathers more light depending on mirror diameter\aperature it seems to follow a larger ball would also reflect more light. I don't have the means to experiment just yet. So It may be that the raw led being limited to simply reflecting off the ball would be sufficient. Then again, the Spitz Patent does call out a lens as Fig. 38 on the diagram for the starball in this thread....
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Post by Ron Walker on Jun 13, 2022 14:15:41 GMT -7
Posted by: charles jones Sep 12 2017, 10:29 PM Thanks, Ron
Charles
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Post by Ron Walker on Jun 13, 2022 14:16:02 GMT -7
Posted by: charles jones Sep 12 2017, 10:48 PM Jamie, I only uploaded the drawings of the Spitz patent. Would you like the worded description? Let me know.
I have no idea the size of the silver ball in the Model B. I don't think the patent mentions that as most patents tend to be broad and non - specific from my point of view. I know from my early experiments, the ball should be as small as possible as I mentioned before. I am thinking 25 mm or less.
There must be something out there, off the shelf, that could be used. That means intensive searching.
It is certainly an interesting approach to pinpoint projection, and obviously worked for the Model B. Is it practical for a small projector, I don't know, but I wanted to try it. It worked for the Spitz STP (? whatever). BTW Spitz only made a couple of these and I had a chance to see one in operation in San Diego years ago. Very impressive star images for pinpoint projection. But then again, so many of the stars were individually lensed and the star globe was massive--maybe 4 to 5 feet in diameter from memory.
Just remembered: Didn't Brent Sullivan (Phoenix) get one of these? Ron?
I think I remember reading that in this forum. If so, he could tell you the diameter of the mirror ball used.
Charles
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Post by Ron Walker on Jun 13, 2022 14:16:26 GMT -7
Posted by: Ron Walker Sep 13 2017, 03:02 PM QUOTE(charles jones @ Sep 12 2017, 10:48 PM) * Jamie, I only uploaded the drawings of the Spitz patent. Would you like the worded description? Let me know. I have no idea the size of the silver ball in the Model B. I don't think the patent mentions that as most patents tend to be broad and non - specific from my point of view. I know from my early experiments, the ball should be as small as possible as I mentioned before. I am thinking 25 mm or less. There must be something out there, off the shelf, that could be used. That means intensive searching. It is certainly an interesting approach to pinpoint projection, and obviously worked for the Model B. Is it practical for a small projector, I don't know, but I wanted to try it. It worked for the Spitz STP (? whatever). BTW Spitz only made a couple of these and I had a chance to see one in operation in San Diego years ago. Very impressive star images for pinpoint projection. But then again, so many of the stars were individually lensed and the star globe was massive--maybe 4 to 5 feet in diameter from memory. Just remembered: Didn't Brent Sullivan (Phoenix) get one of these? Ron? I think I remember reading that in this forum. If so, he could tell you the diameter of the mirror ball used. Charles Brent actually has both. He has the star balls from the original "B" that was originally at the Air Force Academy as well as one of the large star balls like the one in San Diego. The "B" star balls were three feet in diameter and the San Diego type was four feet in diameter. I remember looking inside and both had a fairly large mirror ball at the horizon point. I'm remembering about two inches or perhaps more. For sure is wasn't an inch or so. Here is a picture of the inside of the "B" globe www.observatorycentral.com/index.php?s=&showtopic=3849&view=findpost&p=24225 The packing peenuts are probably 1/2 to 3/4 inch across and the wire is at least 1/2 inch in diameter. View the cable near the top where it has the same distance perspective as the dome mirror. I'm fairly sure the mirror was at least two inches in diameter but could be wrong.
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Post by Ron Walker on Jun 13, 2022 14:16:43 GMT -7
Posted by: charles jones Sep 14 2017, 07:21 PM Based on that photo, I would say you are right, Ron--2" or so.
When I experimented with this type of projection, I noticed that as you move away from the zenith of the ball towards 90 degrees, the image of the light source seemed to change position. My thought was, to minimize this shaft the ball should be small. But apparently this was not a problem in the Spitz projectors.
Anyway, if Jamie gets this working, I'll be anxious to hear the results as I wanted to try this very approach.
Charles
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Post by Ron Walker on Jun 13, 2022 14:17:09 GMT -7
Posted by: Philostopher1 Sep 15 2017, 07:33 PM Project update
Fork Layout
I got most of the fork parts laid out on 1\4" hair cell ABS. I need another 10 square feet... Basically, it is a fork mount scheme similar to Megastar or a moving stage light. The base is the Z axis (for adjustable precession) , the top of the fork is the Y axis for latitude adjustment, and of course the Yoke between the forks holding the star balls is the X axis (diurnal). Through software it should be possible to have any practical diurnal, annual, latitude or precessional motion from any point of view in our solar system. I have no idea how to do the software yet. Presumably, it should be a matter of sine waves relationship calculations. I did some of this through audio synthesisis and laser light show synthesizers using eprom look-up tables and DACs I am thinking in terms of a CNC \ moving stagelight approach... I hope I can use "off the shelf" GRBL or DMX protocol, but I am getting ahead of myself. One small step at a time...
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Post by Ron Walker on Jun 13, 2022 14:17:28 GMT -7
Posted by: moonmagic Sep 16 2017, 09:51 AM You guys are ALL just AMAZING! What a project.
Someone mentioned the original Spitz Model A was plastic. Before going to metal dodec's they were plastic. I have one of those in the "collections." It was much thinner plastic that I would have first imagined, with no lenses used for the brighter stars as they improved when they went to the A-1. I will be forced to eventually find a good way to re-glue or re-join some of the panels as it is having age issues. (Don't even go there!)
Meanwhile, with all this effort expended on making your own, wouldn't you still be looking for one that has become surplus? Every once in a while one still becomes available if you are willing to get a truck and go take one out.
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