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Post by Ron Walker on Apr 21, 2023 11:54:16 GMT -7
Posted by: mrgare5050 Oct 7 2007, 03:44 PM good work reorging some of this ron
you know, im pondering owens words all the more now that ive reread this .. in fact, i need to rerun all 2200 posts here, theres so much that its easy to forget.
but attendance .. live attendance might not be what we think for traditional shows.. for NON traditional shows of the fantastic like you have there owen
that gets us thinking outside the box - what if i could set up a craft assembly line to build small projectors. what if there are different types of events .. i love this kind of probe that gets into original thinking...
gare, wanting to build ANOTHER planetarium... im addicted it seems to BUILDING them not just using them.....
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Post by Ron Walker on Apr 21, 2023 11:54:56 GMT -7
Posted by: Ron Walker Oct 8 2007, 12:23 PM QUOTE(Owen Phairis @ Oct 7 2007, 11:25 AM) * Hi Ron, Yes, even though they said it was light proof, needless to say it was not. sad.gif Well yes, it was a little troublesome not getting the attendance I hoped for. However, the few people that did take the time to see the show loved it! biggrin.gif I think we all need to remember that 'educational show' does not envoke the same emotional response that 'Disneyland' does. I guess that is why I am taking a little different direction from most of you. I am now thinking more in terms of a small permanent science museum specializing in planetarium projectors and the space and physical sciences. It will be interesting to see what path the museum leads me. Allthough it appears to be several years away, I hope to start on the publicity campaign this winter to see if there is any interest. Any ideas? Ron, Are you shooting any HD TV? I was thinking of buying the Sony HDR V1U..... Owen www.pictorialism.comSpitz A1, A3P, Nova III, GOTO s-2 Haven't started any HD TV yet as I'm not impressed with whats been offered so far. Also the editing is a problem as well as what to store the finished programs on. I have not researched the HDR V1U but I would have a hard time believing that a $2K to $3K camera could compete. I personally have two criteria when looking for cameras. The lenses must be manual and the chips must be at least 1/2 inch ones. I must admit that I have been intrigued with the Panasonic AG-HPX500 HD camcorder. I'm just not sure if I want to get stuck with their P2 card technology. Otherwise it's a very good looking camera. I really like your total museum idea. If you have a place for it and there are no zoning problems, I say go for it. You could have a general admission ticket and then extra sub tickets for the lightning show and/or the planetarium. The best thing is that it would be permanent and not rebuilt at every location.
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Post by Ron Walker on Apr 21, 2023 11:55:27 GMT -7
Posted by: jmarmor Apr 11 2008, 11:54 AM QUOTE(Ron Walker @ Dec 18 2006, 06:07 PM) * OK, it's time to start building.
First we must make the gores that the screen will be made out of. You can make as many or as few as you like. Just remember that if you do four you will basically have a box.
FORMULA FOR DOME PATTERN
1-Take desired circumference of the dome, divide that by the number of desired gores to find the width of each gore at the base of the dome.
2-To find your constant: 90 divided by 1/4 of the circumference equals your constant.
3-To find the width of the gore at intervals from the base towards the zenith: a-Multiply the constant by the distance up from the base. b-Find the cosine of that number. c-Multiply the cosine by the width of the gore's base. The answer is your width at the distance up from the base.
An example: Since I wanted as large a dome as possible from the material I had, I went about this a bit backwards. Just follow along.
The material I found came in a roll 52 inches wide. I found that I needed two inches on either side of the gore to make the support collar for the gore. Thus each gore could be 48 inches at the base. I decided to use a total of 14 gores as this made as large a dome as I could build in the space I had available. Thus I am starting the above calculation with a circumference of 672 inches.
As in the above calculation:
1-Desired circumference 672 inches. Total number of gores 14. Thus 672 divided by 14 equals a 48 inch base for each gore.
2-90 divided by 642/4 equals 0.5357 which is my constant for the above dome.
3-a-0.5357(40)=21.428 3-b-cos21.428=0.93088 3-c-0.93088(48inches)=44.6822 or 44 11/16 inches.
If you followed that at all you would understand the each gore has a base that is 48 inches wide and that at a distance of 40 inches up along the gore toward the zenith of the dome, each gore would have a width of 44 11/16 inches. Now it is best to make a template and then cut the material for the gores from the template. Be sure to allow the extra material on both edges to make the support collar. We made calculations for every two inches along the gore's 1/4 circumference of the dome.
The is an example from the calculations for my large dome. Before this was tackled we made a small baby dome to make sure we were doing everything right. Calculations and pictures will follow both on the experimental dome and the full size one as construction begins.
Hi Ron,
I am trying to use the formula you provided, and being a rather mathematically-challenged (i.e. stupid) person, I have a question for you:
When calculating gore width up from the gore base using the steps you listed, when you multiply the constant by the distance up from the base, is the resulting number an angle? When I use online cosine calculators, I am asked to enter an anle, not merely a number. Please clarify!
thanks....
Jason
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Post by Ron Walker on Apr 21, 2023 11:55:56 GMT -7
Posted by: Ron Walker Apr 11 2008, 03:51 PM QUOTE(jmarmor @ Apr 11 2008, 11:54 AM) * Hi Ron, I am trying to use the formula you provided, and being a rather mathematically-challenged (i.e. stupid) person, I have a question for you: When calculating gore width up from the gore base using the steps you listed, when you multiply the constant by the distance up from the base, is the resulting number an angle? When I use online cosine calculators, I am asked to enter an anle, not merely a number. Please clarify! thanks.... Jason No, not an angle, but the width of the gore at that exact point. When laying out a gore template, a line perpendicular to the bottom (spring line point) and terminating at the zenith point is extremely helpful. When using the above formula, the width of the gore at a point 40 inches up from the base is plotted. One must then center this dimension (44 11/16 inches) on the central perpendicular line. Two points, each one (22 11/32 inches) from the line. This is a lot easier to understand with a picture and I will refer you to: www.observatorycentral.com/index.php?showtopic=2180This is an example gore for a ten foot diameter dome made up of 24 gores. As far as angles go, I just put the number into a "scientific calculator" and requested the cosine of that number. Out popped the answer. There are charts in the back of most trig books but they can be a pain to find. I did notice an error however, when I was inputting this information. I inadvertently put the number 642 in step two, it should be 672 from the first step. This was just a typing error as the constant is correct for this size dome. It should read: 2 - 90 divided by 672/4 equals 0.5357 which is my constant for the above dome. Or 672/4 = 168. Then 90/168 = 0.5357 which is the constant. I will correct the post. If you give me the diameter of the dome you want to build and the number of gores, I will work out the calculations if you like.
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Post by Ron Walker on Apr 21, 2023 11:56:33 GMT -7
Posted by: jmarmor Apr 11 2008, 04:24 PM QUOTE(Ron Walker @ Apr 11 2008, 04:51 PM) * No, not an angle, but the width of the gore at that exact point. When laying out a gore template, a line perpendicular to the bottom (spring line point) and terminating at the zenith point is extremely helpful. When using the above formula, the width of the gore at a point 40 inches up from the base is plotted. One must then center this dimension (44 11/16 inches) on the central perpendicular line. Two points, each one (22 11/32 inches) from the line. This is a lot easier to understand with a picture and I will refer you to: www.observatorycentral.com/index.php?showtopic=2180This is an example gore for a ten foot diameter dome made up of 24 gores. As far as angles go, I just put the number into a "scientific calculator" and requested the cosine of that number. Out popped the answer. There are charts in the back of most trig books but they can be a pain to find. I did notice an error however, when I was inputting this information. I inadvertently put the number 642 in step two, it should be 672 from the first step. This was just a typing error as the constant is correct for this size dome. It should read: 2 - 90 divided by 672/4 equals 0.5357 which is my constant for the above dome. Or 672/4 = 168. Then 90/168 = 0.5357 which is the constant. I will correct the post. If you give me the diameter of the dome you want to build and the number of gores, I will work out the calculations if you like. Ron - Thanks so much for the information. I had noticed the error you mentioned, and am glad you verified it. Since you are offering (Wow!), I am interested in getting dimensions for a 10 foot diameter dome with only 10 gores (rather than 24), since I am interested in using cloth or vinyl and minimizing the number of seams to deal with. That would be fantastic if you are able to make the gore width calculations. Hopefully I could reciprocate in the future. Thanks! Jason Marmor
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Post by Ron Walker on Apr 21, 2023 11:59:20 GMT -7
Posted by: Ron Walker Apr 11 2008, 05:32 PM QUOTE(jmarmor @ Apr 11 2008, 04:24 PM) * Ron - Thanks so much for the information. I had noticed the error you mentioned, and am glad you verified it. Since you are offering (Wow!), I am interested in getting dimensions for a 10 foot diameter dome with only 10 gores (rather than 24), since I am interested in using cloth or vinyl and minimizing the number of seams to deal with. That would be fantastic if you are able to make the gore width calculations. Hopefully I could reciprocate in the future.
Thanks!
Jason Marmor
Basic info for your dome size.
Diameter 10 feet = circumference 31.4 feet.
10 gores 3.14 feet each or 37.68 inches at the spring line.
Your constant is 0.9554
I will do the calculations tonight for the various distances as per the full length of each gore of 94 1/4 inches. I will do them for every five inches in height like the 24 gore dome. If it looks like a large change in gore width at the top because of the larger starting spring line, I will do some extra where the change is greatest.
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Post by Ron Walker on Apr 21, 2023 11:59:51 GMT -7
Posted by: jmarmor Apr 12 2008, 06:24 AM QUOTE(Ron Walker @ Apr 11 2008, 06:32 PM) * Basic info for your dome size.
Diameter 10 feet = circumference 31.4 feet.
10 gores 3.14 feet each or 37.68 inches at the spring line.
Your constant is 0.9554
I will do the calculations tonight for the various distances as per the full length of each gore of 94 1/4 inches. I will do them for every five inches in height like the 24 gore dome. If it looks like a large change in gore width at the top because of the larger starting spring line, I will do some extra where the change is greatest.
That's fantastic, Ron - Hopefully others can use this information also. I'll get started on mine in the near future, and probably make a scaled down model first.
By the way, I've been toying with an idea for making exterior ribs, which would first require finding a suitable cylindrical object (water tank???) of the appropriate diameter, then coiling heavy gauge wire (like that used for coat hangers, only MUCH thicker) around it, then cutting it into semicircles. The semicircular pieces of wire could then be cut into quarter circle pieces to serve as ribs, and inserted into a small disk of wood at the apex. Obviously, one would have to find a method of attaching the ribs of the exoskeleton to the cloth gores (sleeves or rings perhaps). Four of the semi circles could be joined byfriction fitting metal tubes to create a skirt or base ring, possibly with socket tubes attached (by welding? or epoxy??) at the appropriate intervals to hold the gore ribs. This design would allow the base and apex disk to be attached as needed, and the entire dome to be collapsed/folded when not in use. I haven't read all the older posts, so perhaps I am reinventing the wheel.
Regards,
Jason
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Post by Ron Walker on Apr 21, 2023 12:00:18 GMT -7
Posted by: Ron Walker Apr 12 2008, 11:47 AM 10 foot diameter with 10 gores. Circumference 31.416 feet = 376.99 inches 1/4 circumference = 94.25 inches which is the length of each gore from spring line to zenith.
From the base (spring line) in inches = B+(inches) Width of gore in inches (1/2 on either side of a perpendicular line running from the center of the base [spring line] to top of gore) = W
B+ ~ W
0 ~ 37.699 5 ~ 37.568 10 ~ 37.177 15 ~ 36.527 20 ~ 35.624 25 ~ 34.474 30 ~ 33.084 35 ~ 31.465 40 ~ 29.628 45 ~ 27.585 50 ~ 25.35 55 ~ 22.94 60 ~ 20.37 65 ~ 17.659 70 ~ 14.825 72 ~ 13.662 74 ~ 12.483 76 ~ 11.291 78 ~ 10.086 80 ~ 8.87 82 ~ 7.6437 84 ~ 6.4092 86 ~ 5.1676 88 ~ 3.9202 90 ~ 2.668 92 ~ 1.4138 94.25 ~ point
These are the exact widths for the dome described and DO NOT allow any extra material for either overlap (if welding plastic) or a seam (if sewing fabric). You must decide what type of support structure you want. In my small experimental dome I allowed for extra material so that support ribs could be contained.
Also note that the widths of each gore get rather small as you approach the zenith. A central support core usually occupies this space and I would suggest ending the dome material before you reach this point. A circle of white poster board would cover this "hole" in the dome and the entire area where the most sewing would normally be done.
If you go back to the very beginning of this thread you will see a small experimental dome with this type of support. Actually my dear wife has sewn together a much larger one approximately 18 feet in diameter which I plan on using 1/2 inch plastic water pipe for supports. It is actually all put together in four sections of four gores each as I'm not at all sure if an entire dome could be handled at once. My thought was to erect each quarter and then have small velcro patches to hold the four joints together. All of my free time has been used up working on my projectors and I have not attacked the dome. I will need to do this just to see how well it works.
Anyway, I would add an extra two inches to both sides of each gore to allow for sewing at the proper point and then making a loop in which to slide a support strut. I will take some pictures next week to show you what I mean. Right now taxes call (ugh).
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Post by Ron Walker on Apr 21, 2023 12:00:48 GMT -7
Posted by: jmarmor Apr 12 2008, 09:26 PM QUOTE(Ron Walker @ Apr 12 2008, 12:47 PM) * 10 foot diameter with 10 gores. Circumference 31.416 feet = 376.99 inches 1/4 circumference = 94.25 inches which is the length of each gore from spring line to zenith.
From the base (spring line) in inches = B+(inches) Width of gore in inches (1/2 on either side of a perpendicular line running from the center of the base [spring line] to top of gore) = W
B+ ~ W
0 ~ 37.699 5 ~ 37.568 10 ~ 37.177 15 ~ 36.527 20 ~ 35.624 25 ~ 34.474 30 ~ 33.084 35 ~ 31.465 40 ~ 29.628 45 ~ 27.585 50 ~ 25.35 55 ~ 22.94 60 ~ 20.37 65 ~ 17.659 70 ~ 14.825 72 ~ 13.662 74 ~ 12.483 76 ~ 11.291 78 ~ 10.086 80 ~ 8.87 82 ~ 7.6437 84 ~ 6.4092 86 ~ 5.1676 88 ~ 3.9202 90 ~ 2.668 92 ~ 1.4138 94.25 ~ point
These are the exact widths for the dome described and DO NOT allow any extra material for either overlap (if welding plastic) or a seam (if sewing fabric). You must decide what type of support structure you want. In my small experimental dome I allowed for extra material so that support ribs could be contained.
Also note that the widths of each gore get rather small as you approach the zenith. A central support core usually occupies this space and I would suggest ending the dome material before you reach this point. A circle of white poster board would cover this "hole" in the dome and the entire area where the most sewing would normally be done.
If you go back to the very beginning of this thread you will see a small experimental dome with this type of support. Actually my dear wife has sewn together a much larger one approximately 18 feet in diameter which I plan on using 1/2 inch plastic water pipe for supports. It is actually all put together in four sections of four gores each as I'm not at all sure if an entire dome could be handled at once. My thought was to erect each quarter and then have small velcro patches to hold the four joints together. All of my free time has been used up working on my projectors and I have not attacked the dome. I will need to do this just to see how well it works.
Anyway, I would add an extra two inches to both sides of each gore to allow for sewing at the proper point and then making a loop in which to slide a support strut. I will take some pictures next week to show you what I mean. Right now taxes call (ugh).
Ron - that was incredibly helpful - thanks so much.
Jason
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Post by Ron Walker on Apr 21, 2023 12:01:26 GMT -7
Posted by: mrgare5050 Apr 14 2008, 04:23 AM FORMULA FOR DOME PATTERN
1-Take desired circumference of the dome, divide that by the number of desired gores to find the width of each gore at the base of the dome.
2-To find your constant: 90 divided by 1/4 of the circumference equals your constant.
3-To find the width of the gore at intervals from the base towards the zenith: a-Multiply the constant by the distance up from the base. b-Find the cosine of that number. c-Multiply the cosine by the width of the gore's base. The answer is your width at the distance up from the base.
An example: Since I wanted as large a dome as possible from the material I had, I went about this a bit backwards. Just follow along.
The material I found came in a roll 52 inches wide. I found that I needed two inches on either side of the gore to make the support collar for the gore. Thus each gore could be 48 inches at the base. I decided to use a total of 14 gores as this made as large a dome as I could build in the space I had available. Thus I am starting the above calculation with a circumference of 672 inches.
As in the above calculation:
1-Desired circumference 672 inches. Total number of gores 14. Thus 672 divided by 14 equals a 48 inch base for each gore.
2-90 divided by 642/4 equals 0.5357 which is my constant for the above dome.
3-a-0.5357(40)=21.428 3-b-cos21.428=0.93088 3-c-0.93088(48inches)=44.6822 or 44 11/16 inches.
Hey Ron and Jason. OK if I extract the above as a 'standard reference', like the 'drill bit table' im trying to catalog just some basics like this (lord kows i never calculate anything) on HPAs website for those who take this approach. OC provides reallife stories of building this stuff, but tables/formulas (ken dont you have a light bulb table, whered that go again) tend to get lost midst the posts so im trying occasionally to airlift some of these 'standards out.
gore.. i mean gare
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Post by Ron Walker on Apr 21, 2023 12:02:23 GMT -7
Posted by: Ron Walker Apr 14 2008, 10:42 AM QUOTE(mrgare5050 @ Apr 14 2008, 04:23 AM) * FORMULA FOR DOME PATTERN 1-Take desired circumference of the dome, divide that by the number of desired gores to find the width of each gore at the base of the dome. 2-To find your constant: 90 divided by 1/4 of the circumference equals your constant. 3-To find the width of the gore at intervals from the base towards the zenith: a-Multiply the constant by the distance up from the base. b-Find the cosine of that number. c-Multiply the cosine by the width of the gore's base. The answer is your width at the distance up from the base. An example: Since I wanted as large a dome as possible from the material I had, I went about this a bit backwards. Just follow along. The material I found came in a roll 52 inches wide. I found that I needed two inches on either side of the gore to make the support collar for the gore. Thus each gore could be 48 inches at the base. I decided to use a total of 14 gores as this made as large a dome as I could build in the space I had available. Thus I am starting the above calculation with a circumference of 672 inches. As in the above calculation: 1-Desired circumference 672 inches. Total number of gores 14. Thus 672 divided by 14 equals a 48 inch base for each gore. 2-90 divided by 642/4 equals 0.5357 which is my constant for the above dome. 3-a-0.5357(40)=21.428 3-b-cos21.428=0.93088 3-c-0.93088(48inches)=44.6822 or 44 11/16 inches. Hey Ron and Jason. OK if I extract the above as a 'standard reference', like the 'drill bit table' im trying to catalog just some basics like this (lord kows i never calculate anything) on HPAs website for those who take this approach. OC provides reallife stories of building this stuff, but tables/formulas (ken dont you have a light bulb table, whered that go again) tend to get lost midst the posts so im trying occasionally to airlift some of these 'standards out. gore.. i mean gare Use anything you like that I've put here. Perhaps all should be published in an issue of the HPA so people can have a hard copy. Speaking of a drill bit table. has anyone ever actually determined the sizes of drill bits based on the area of the hole drilled. Since each magnitude is approximately 2.5 times brighter then the next, would that mean the the area of the hole drilled would need to be 2.5 times as big? If that is the case, then a very accurate table could be set up that included drills for various points (tenths) of magnitude. I often hear that a number 80 drill is for a 5th magnitude star, but I'm wondering if that is really correct. I'm beginning to believe that a number 80 drill is more for a 5.5 magnitude star and then we go up from there. I have seen drills smaller then #80 advertised but I could not imagine trying to drill with them. I'm thinking that #80 is the smallest practical drill that one can work with. I'm also thinking that if the holes get much smaller then refraction would start to take place and the projections would actually get bigger. If indeed 5.5 magnitude (or 5th magnitude for that matter) stars are assigned to a #80 drill, then 1st and 2nd magnitude ones would surely need lenses or the stars would look like our Sun. The S&T article on Steve Smith's projector and my own observations on the Spitz A3P star ball really started me thinking about this. Since Steve Smith worked in a museum with an A3P, I'm wondering if he used it for his basis on star holes, since it appears his choices of hole diameters matches those of the A3P. The article is somewhat vague on the exact size of drill for most of the star magnitudes and a bit more effort needs to go into final design goals. The only time I ever read of magnitude numbers down to the tenth is in articles about Zeiss caliber projectors. I have come to the conclusion though, that a #80 drill is probably used for those stars of magnitude 5.5 as both Smith and Spitz make mention of adding many more stars past 5.0 which appears to be the original design criteria. Perhaps once one get fainter then 5th magnitude, the projected stars look just about the same, but nowhere that I've found really accurately states exact star sizes. I need to do some more research on this as I don't think a definitive chart has ever been published. It would also be interesting to measure the actual iris diameter of a camera lens as each stop equals twice as much light. Then (if my lopsided thinking is correct) each star full magnitude is equal to 2.5 stops. That would mean a 15 stop difference between Sirius and a 5th magnitude star. Is this the same area as the difference between a 1/4 inch hole and that made by a #80 drill? ?
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Post by Ron Walker on Apr 21, 2023 12:02:50 GMT -7
Posted by: Owen Phairis Apr 14 2008, 01:22 PM Here is a photograph of a couple of geodesic domes that Pioneer setup and was using for demo purposes this past weekend. The picture was taken before the audience was allowed in. Inside the large dome was a full dome video projection system and some very loud music.
Owen
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Post by Ron Walker on Apr 21, 2023 12:03:09 GMT -7
Posted by: Ron Walker Apr 14 2008, 05:05 PM QUOTE(Owen Phairis @ Apr 14 2008, 01:22 PM) * Here is a photograph of a couple of geodesic domes that Pioneer setup and was using for demo purposes this past weekend. The picture was taken before the audience was allowed in. Inside the large dome was a full dome video projection system and some very loud music.
Owen
How did they support the dome material from the outer geodesic structure in the left dome?
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Post by Ron Walker on Apr 21, 2023 12:03:31 GMT -7
Posted by: Owen Phairis Apr 14 2008, 05:16 PM QUOTE(Ron Walker @ Apr 14 2008, 05:05 PM) * How did they support the dome material from the outer geodesic structure in the left dome?
Looks like a pretty simple design....
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Post by Ron Walker on Apr 21, 2023 12:03:51 GMT -7
Posted by: Ron Walker Apr 14 2008, 07:07 PM QUOTE(Owen Phairis @ Apr 14 2008, 05:16 PM) * Looks like a pretty simple design....
I really like the simplicity and strength of that. If one just added a little positive air pressure on the inside, it would hold the dome up and round as well as keeping most of the dust out. If the air supply gave out, the dome would just sag a bit to these chain supports. Nothing would ever fall on the audience. Very nice design indeed.
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