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Post by Ron Walker on Oct 21, 2022 10:42:30 GMT -7
Posted by: sgrijalva Apr 6 2021, 08:56 PM QUOTE(Scott T @ Apr 5 2021, 02:13 PM) * You may have noticed a pause in the posts - I have hit a simple but time consuming problem. I have settled on 19000 stars at the moment -about 600 stars per plate. The spreadsheet sorts the stars to the correct plates in an instant. However, there are around 5000 stars duplicated on more than one star plate (in the overlapping zones of the pates). I do not want to keep the duplicate stars because if they don't align perfectly (very likely) there will be a higher density of stars in the overlapping regions and if they do align perfectly the stars will be double brightness. Hi, A solution to the problem could be implemented with some algorithm to determine if a star is inside the polygon. There are several algorithms to determine if a point is within a polygon. g.co/kgs/vAfaf5Point in polygon (PIP). I found this code that can work, it needs the number of vertices of the polygon, and the coordinates of each of the vertices apart from the coordinates of the point to search, in this case the coordinates of the star . wrf.ecse.rpi.edu/Research/Short_Notes/pnpoly.htmlThe code is in C. In the end, instead of having a circle full of stars, we will have the figure of the polygon delineated by the same stars as in this stellar plate of the Ohira planetarium. (Mega-Stars) Saul
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Post by Ron Walker on Oct 21, 2022 10:42:46 GMT -7
Posted by: Ron Walker Apr 7 2021, 09:17 AM This stuff is so far above me I would black out from lack of oxygen. I'm still trying to get my head around the effects of projection and reversing the image but I guess that's the simple part. At one time I actually understood differential equations but they went with my youth and unuse. Now I'm lucky if I can still add and subtract. I guess it must be tax time.
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Post by Ron Walker on Oct 21, 2022 10:43:07 GMT -7
Posted by: Scott T Apr 12 2021, 12:08 AM Thanks Ron and Saul- sorry I have been a bit busy the last few days.
Ron- having settled on 19k stars I have since been thinking about reducing the numbers down in the first instance in line with your recent post. I am going to try to have the capacity to be able to swap the star plates out. The project will stand a better chance of success if I start with more manageable star plates -make the mistakes on those before making plates with huge numbers of stars.
Saul - thank you for the 'Point in Polygon' method. It proves there is always more than one way to skin a cat! That PIP method certainly looks like the most professional and concise way to approach this whole problem. I have to admit I had searched for methods of solving this problem but had not found the answer. It goes to show that you need to use the right terminology to get useful search results.
My programming skills are clunky so my plan is to press on with the spreadsheet as I am so close to the finishing line - but in slow time I will have a look at the PIP method. That opens up the path to a piece of code where you can select the number of stars you want and it churns out the star plates automatically, hmmm... another challenge!
It is interesting to note that the Megastar screen shot is a ditrigon rather than a hexagon- i.e. they are using the isodistant form of the truncated icosahedron. It still leaves me puzzling about the tesselation problem - With non-overlapping star plates the pentagonal faces would need to be inverted to avoid gaps in the star field.
I have another question for Ron (if you don't mind). I can't tell from the photos in your thread - the Minolta star plates are clearly circular disks - but is the pattern of stars punched into them circular too or do they form hexagons/ pentagons/ ditrigons?
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Post by Ron Walker on Oct 21, 2022 10:43:26 GMT -7
Posted by: Ron Walker Apr 12 2021, 07:55 PM QUOTE(Scott T @ Apr 12 2021, 12:08 AM) * Thanks Ron and Saul- sorry I have been a bit busy the last few days.
Ron- having settled on 19k stars I have since been thinking about reducing the numbers down in the first instance in line with your recent post. I am going to try to have the capacity to be able to swap the star plates out. The project will stand a better chance of success if I start with more manageable star plates -make the mistakes on those before making plates with huge numbers of stars.
Saul - thank you for the 'Point in Polygon' method. It proves there is always more than one way to skin a cat! That PIP method certainly looks like the most professional and concise way to approach this whole problem. I have to admit I had searched for methods of solving this problem but had not found the answer. It goes to show that you need to use the right terminology to get useful search results.
My programming skills are clunky so my plan is to press on with the spreadsheet as I am so close to the finishing line - but in slow time I will have a look at the PIP method. That opens up the path to a piece of code where you can select the number of stars you want and it churns out the star plates automatically, hmmm... another challenge!
It is interesting to note that the Megastar screen shot is a ditrigon rather than a hexagon- i.e. they are using the isodistant form of the truncated icosahedron. It still leaves me puzzling about the tesselation problem - With non-overlapping star plates the pentagonal faces would need to be inverted to avoid gaps in the star field.
I have another question for Ron (if you don't mind). I can't tell from the photos in your thread - the Minolta star plates are clearly circular disks - but is the pattern of stars punched into them circular too or do they form hexagons/ pentagons/ ditrigons?
They are not perfect but I would say they are closer to hexagons, pentagons, then a circle.
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Post by Ron Walker on Oct 21, 2022 10:43:47 GMT -7
Posted by: Ron Walker Apr 13 2021, 09:23 AM QUOTE(Ron Walker @ Apr 12 2021, 07:55 PM) * They are not perfect but I would say they are closer to hexagons, pentagons, then a circle.
From the Helmut Werner book "From The Aratus Globe To The Zeiss Planetarium" comes this:
More proof that the star plates are not round projections.
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Post by Ron Walker on Oct 21, 2022 10:44:07 GMT -7
Posted by: moonmagic Apr 21 2021, 03:30 PM QUOTE(Ron Walker @ Apr 13 2021, 10:23 AM) * From the Helmut Werner book "From The Aratus Globe To The Zeiss Planetarium" comes this:
More proof that the star plates are not round projections. While all interesting, much like Ron said, but in my case almost all of this is above me. None the less, I try to follow along as best I can. My interest is that I am reading about someone with the knowledge of how to approach this and can actually build it. Meanwhile, I too have always wondered about the need for so many stars. Once you are beyond what the human eye can see without a telescope say more than 6th magnitude what is to be gained for reproduction of the "artificial sky? Meanwhile, as is likely clear by now, I majored in lunch and recess in school. mm
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Post by Ron Walker on Oct 21, 2022 10:44:26 GMT -7
Posted by: Ron Walker Apr 21 2021, 04:28 PM QUOTE(moonmagic @ Apr 21 2021, 03:30 PM) * While all interesting, much like Ron said, but in my case almost all of this is above me. None the less, I try to follow along as best I can. My interest is that I am reading about someone with the knowledge of how to approach this and can actually build it. Meanwhile, I too have always wondered about the need for so many stars. Once you are beyond what the human eye can see without a telescope say more than 6th magnitude what is to be gained for reproduction of the "artificial sky? Meanwhile, as is likely clear by now, I majored in lunch and recess in school. mm
I have a hard enough time seeing the 6th magnitude ones in the dome. The only possible use is if you can not see the extremely faint ones without some kind of optical aid.
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Post by Ron Walker on Oct 21, 2022 10:44:45 GMT -7
Posted by: sgrijalva Apr 22 2021, 02:26 PM Hello everybody, In the last few months I have been doing internet research on planetariums on Japanese sites. I have reviewed many sites, especially Japanese schools, because it seems that, in Japan, planetarium building is a national sport.
Among so many sites I found software and a set of spreadsheets to generate star plates. I spent many weeks trying to figure out the meaning of the labels and buttons on the interface, but finally got it to work yesterday afternoon.
You can make the plates for both spherical planetarium with segments and for planetariums in the shape of a truncated icosahedron. By feeding the program I was able to obtain a star plate. They are circular in shape depending on the required visual field, but then superimpose the image of either a pentagon or a di trigon as the case may be.
The spreadsheets have the information of the coordinates of both the center of each figure and that of the vertices in spherical coordinates, as well as a catalog of stars.
There is a small section in the program that is in charge of handling the magnitudes and their representation in the generated image that I still haven't figured out how it works. The little program generates low quality BMP files for visualization and SVG files for high resolution.
In the images you can see the tables with the coordinates of each face of the truncated icosahedron, that of each vertex and the catalog of stars.
Greetings Saul
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Post by Ron Walker on Oct 21, 2022 10:45:08 GMT -7
Posted by: sgrijalva Apr 22 2021, 02:28 PM Here are samples of the starplates
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Post by Ron Walker on Oct 21, 2022 10:45:24 GMT -7
Posted by: sgrijalva Apr 22 2021, 02:30 PM Here more starplates diferent coordinates. pentagon and irregular hexagon (ditrigon).
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Post by Ron Walker on Oct 21, 2022 10:45:42 GMT -7
Posted by: Scott T Apr 25 2021, 12:33 AM Thanks Saul - that is really good. Are you able to share the link and the instructions?
It is encouraging to think that it is a more popular activity in Japan.
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Post by Ron Walker on Oct 21, 2022 10:45:57 GMT -7
Posted by: sgrijalva Apr 25 2021, 07:02 AM Sure Scott, no problem. I am going to share a drive in Google with all the files and I will share the link. I hope to do it in the course of the day.
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Post by Ron Walker on Oct 21, 2022 10:46:14 GMT -7
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Post by Ron Walker on Oct 21, 2022 10:46:35 GMT -7
Posted by: moonmagic Apr 26 2021, 01:54 PM QUOTE(Scott T @ Apr 25 2021, 01:33 AM) * Thanks Saul - that is really good. Are you able to share the link and the instructions?
It is encouraging to think that it is a more popular activity in Japan.
Scott, Because of Goto Optical and Minolta Optical, Japan may have more planetariums than a number of other countries. They are everywhere and many are elaborate. They also believe in many cultural centers for the people. Japan has always been heavy into all forms of education especially mathematics and the sciences. The Goto company also makes (or did at one time) very fine optical telescopes including very professional level observatory scopes. I don't know if Goto every branched into the medical field for hospital level microscopes as Zeiss (Germany) did years ago.
MEANWHILE, I hope this program this gentlemen has found is useful to you in your work. mm
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Post by Ron Walker on Oct 21, 2022 10:46:55 GMT -7
Posted by: sgrijalva Apr 27 2021, 10:24 AM Hello, I have included a small guide to use the sss2008 program because it is in Japanese. It is where it took me a long time to deduce each of the inputs to the program to generate the graphs. Greetings.
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