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Forum Support Admin
Posts: 3118
  
Location: Wyoming Sagebrush | Looks like it might be the cats meow.
A long series of replies, but every time I catch up with it I get more intrigued.
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Board/ccd... |
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Forum Admin
Posts: 1216
Location: Cedar Park, Texas | I have one of those on its way to me even now. It should be here any day. I must say...this is a major departure from the run-o-the-mill Hartmann mask. I can't wait to try it out!!
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Forum Support Admin
Posts: 3118
Location: Wyoming Sagebrush | Did you order one from Wunderlin?
I have to go to the doctor next week so while I'm in town I'm going to try and find somewhere I can get the JPEG Adam left blown up to about 14" diameter.
Then try and cut one out of something suitable and make some sort of frame for it.
I sure liked how the pattern looked in that cool little video clip.
This could be a revolutionary idea! |
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Expert Junky
Posts: 2686
 
Location: Marysville,Wa 48.07N-122.21W | Hey guys!  I've been following that thread from July. Looks like just the ticket! It certainly leaves no doubt as to when everything is in focus!
Do you have a link to the source?  |
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Forum Support Admin
Posts: 3118
Location: Wyoming Sagebrush | Ron,
There are some links in the CN thread to some Russian sites where the design is discussed and I guess they can be translated.
I blew up a drawing from the CN thread, but the scale was wrong. From the discussion I gathered an angle of 40° was needed for the bars, but I measured it from some of the pics shown and it seem to be about 20°, maybe they meant an included angle?
I'm going to get out my drafting tools and see if I can draw a pattern for my 12.5 inch. Looks like the basic formula is focal length divided by 150 to come up with a measurement for a bar plus the space next to it, or a figure to divide by half to get the bar width and slit width. For my 1430mm FL I end up with about 9.5mm, so I guess I'll use 5mm as a measurement.
Then see what I have around here to cut one out of.
Boy, it would be nice to get a focus that you "knew" was dead on. Even with the dial indicator I use, I still end up taking lots of shots trying to compare them to decide which is best. Would sure beat buying a Stiletto and you can't use one of those with a camera/lens setup. |
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Expert Junky
Posts: 2686
Location: Marysville,Wa 48.07N-122.21W | Just found the link to this product:
http://www.spike-a.com/
I think this could definately be a hit! |
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Veteran Junky
Posts: 113
Location: Lexington NC | Would it surprise anyone here that the manufacture of the Spike-a mask was a shot glass junkie? 
I have posted my math formula on the Russian forum that the original design was posted. The calculus formula has been difficult for a lot of people to follow along.
When I posted results of my mask I was asked...no.. begged to please make masks for the public. It has taken a while to contact Pavel Bahtinov about permission to call the mask a Bahtinov mask. My e-mails went to his spam folder.
I didn't want a post that sounded like an ad, so I have been hesitant to comment here. But before this thread gets caught up into some of the issues with the math and how the thing works, let me make a few points.
Here is my simple math formula to calculate the cutouts: Take your clear aperture size and divide by 35. Yes it is that simple!!. That will give you a cutout size and spacing for the horizontal side. for the angled side multiply your cutout by 1.05. This will widen the diffraction spikes on the angled side. I used 21.4 degrees. Here is why- I drew my first prototypes with a cad program. I simple drug the angle up until the third order spectrum area of the spike had a very small gap to the center diffraction spike. This helps get that spot on focus that we are looking for.
That is it in a nutshell. I will work with Andy on a full "Shotglass method for the non-gazillionaires" for Junkies here to make a mask of your own.
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Forum Support Admin
Posts: 3118
Location: Wyoming Sagebrush | So, how is "Farmer Dave" connected? I've been trying his mask generator, but I've been looking at a full aperture mask which would be about 15" diameter.
Lot of cutting to make that thing, so now I'm thinking of making an off axis version. Which ought to work, I can still get to about 6". |
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Veteran Junky
Posts: 113
Location: Lexington NC | I don't know farmer Dave, just have seen his post of a very nice program to do the math and export a .svg file. He has links world wide and even one on the Russian forum. I sure could have used this. I had to get out my old calculus books and decipher the formula.
Tip on cutting- make all cuts straight and free of burrs.
John- explain your off axis version. |
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Forum Support Admin
Posts: 3118
Location: Wyoming Sagebrush | Well, I haven't gotten very far. I'm still basically shut down waiting on a new set of RA motors, but Since my main scope is a newt, I figured I'd see how that generator would produce a pattern for say a 6" aperture at the focal length of my newt.
I was going to make some test masks of some sheet ABS plastic I have and then when I get one that works like it should, mill it out of something like sheet aluminum about the thickness of the stuff traffic signs are made of. Should mill pretty easy with a carbide aluminum full flute end mill.
I dunno, this thing is so new, I'm not sure where I'll end up. The CN thread is getting so long, it's hard to keep up with all the comments. My math is soooo rusty, I'm doing my usual back pocket SWAG engineering! |
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Any of you guys seen this focusing rig?