FarmerDave
sage
Reged: 09/07/07
Posts: 412
Loc: Northern Virginia
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Sunday update: the mo' better Bahtinov Mask Generator version 0.3!
- Fixed a misspelling of Bahtinov in the name of the generated file. Sorry Pavel, and thanks to John W. for pointing it out.
- Fixed a bug in which the "horizontal stripe count" was not actually being recognized. Thanks to Kevin R. (chupacabra) for spotting it and not beating me up about it.
- Reordered the XML comments in the SVG file so that the parameters that are entered appear at the top of the comments section, in the order they are entered in the generator form.
About that last bit - SVG files are a flavor of XML, which is a text-based format. The practical upshot of which is that you can open the SVG file with any text editor.
I'm actually emitting the parameters entered (as well as some calculated values) as XML comments - you'll see them toward the bottom as text surrounded by <!-- -->. So, if you can't remember what the values you used to generate a given file are, just open it in a text editor - or, if you're viewing an SVG file in Firefox, just right click an select "View Page Source," then scroll to the bottom.
I'm somewhat amused to see that I'm getting hits from all over the world, including via automatic translators - I wonder how well "yada, yada, yada" in my lame non-EULA translates. 
David
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Celestron C6/C9.25/CG-5GT Mount
Orion 80ED/EON 72/Supercharged Atlas EQ-G
Garrett Optical Signature Series 10x50
Canon XTi (soon to be modded)/Canon 40D (unmodded)
Meade DSI/Meade DSI Pro/Philips SPC900N
1944 Ford 2N/1948 Ford 8N
Bahtinov Mask Generator * AstroCataLink * 40DShutterCount
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Jerry3672
Vendor - Quantum Astronomy Products
Reged: 01/20/08
Posts: 498
Loc: Lexington NC
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Quote:
I'm somewhat amused to see that I'm getting hits from all over the world, including via automatic translators - I wonder how well "yada, yada, yada" in my lame non-EULA translates.
David
You Rock Farmer of the Dave!(automatically translated)  Everyone world wide likes the Bahtinov mask generator.  Here is a short list of places talking about the Bahtinov mask and your generator:
Russia http://www.astronomy.ru/forum/index.php?topic=10421.300
USA- http://www.telescopejunkies.com/forums/thread-view.asp?tid=1562&posts=10&start=1
Amsterdam- http://www.astroforum.nl/post166678.html
Greek - http://astroforum.gr/forum/viewtopic.php?31072&sid=b786d9a7908fe4f2e1d78f78f6f5a7cb
Thai- http://www.darasart.com/webboard/Question.asp?
ID=3189
Australia http://www.iceinspace.com.au/forum/showthread.php?p=363399
Spain http://www.asociacionhubble.org/modules.php?name=Forums&file=viewtopic&t=27601
UK http://stargazerslounge.com/index.php/topic,30884.50.html
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Meade LXD75-SN-8, SN-10, C11
DSI Pro
Canon XSi 450D unmod
www.spike-a.com Bahtinov Style Focus Mask
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groz
Pooh-Bah
Reged: 03/14/07
Posts: 1038
Loc: Duncan, BC
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When I use the generator, V0.3 (or the output from any previous ones), and pull them into inkscape, they look great. BUT, then from inkscape, write a dxf to take to the cutting shop, the dxf is just useless junk. BUT, if I take the original ones that snowdragon was emailing around, and save those as a dxf, they appear to be useable.
What is the difference ???
It's easy to see, just save one from the generator and pop it up in inkscape, save as a dxf, then load the dxf into irfanview, it'll show the issue. When irfan is happy with the dxf, then the cutting shop appears to be.
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FarmerDave
sage
Reged: 09/07/07
Posts: 412
Loc: Northern Virginia
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Quote:
BUT, then from inkscape, write a dxf to take to the cutting shop, the dxf is just useless junk.
Yeah, I wrote about that a few posts ago. Here's an excerpt:
Quote:
<FARMERDAVE>
Just to see what happened, I tried to convert the SVG to DXF using a couple of different programs - it wasn't pretty. In one case, the conversion converted the curves in the wrong direction, and in another, the clipping paths weren't honored, so the DXF ended up with lines all over the place where they didn't belong, so it took a good bit of manual editing to get it right.
</FARMERDAVE>
The second program of which I was speaking was Inkscape.
Quote:
What is the difference ???
The difference is that I'm calculating the cutouts' positions, mapping them onto a big square, and relying on a circular mask to constrain them. I'm auto-generating W3C "standard" SVG, and apparently Inkscape's DXF generation routine doesn't quite have enough information and/or smarts to do a good translation.
Adam actually drew his template in Inkscape - so it knew how to join the lines, and the order in which he did things, etc. I'm guessing that it in that case it "knows" enough to make a clean translation.
If it's useless to you - sorry. Personally, I found generating the SVG, then editing the DXF file to take out the extra lines a lot less work than trying to draw one from scratch.
At this point, I'm not sure what - if anything - I can do to rectify the situation, but I haven't given it a lot (er, any) thought/time/effort. If/when I come up with something, I'll be sure to post it here.
David
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Celestron C6/C9.25/CG-5GT Mount
Orion 80ED/EON 72/Supercharged Atlas EQ-G
Garrett Optical Signature Series 10x50
Canon XTi (soon to be modded)/Canon 40D (unmodded)
Meade DSI/Meade DSI Pro/Philips SPC900N
1944 Ford 2N/1948 Ford 8N
Bahtinov Mask Generator * AstroCataLink * 40DShutterCount
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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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Hey Groz - As David said his generator puts the drawing together a bit differently. Basically, David's drawings are a conglomeration of objects and mine is a combination of several paths. The generated drawings can be converted, but they need to go through some post processing (kind of like our astro photos  ). If the cutting shop you are using can not convert or use the svg files then let me know. Send me an email with the generated drawing and I'll have a go at converting it for you. Of course, you will owe me big... I am thinking something like a 30" Obsession. OK, a little extreme, how about just a 12"? 
Cheers!
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Adam
12" LX200R, AT80LE
Lunt 60mm Ha & CaK solar scopes
DMK41.AS, DSI Pro, DSI-C, LPI
Denver Astronomical Society
Brighton Astronomical Group
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cvedeler
Carpal Tunnel
Reged: 12/20/05
Posts: 2124
Loc: Scottsdale, AZ
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How to not do astrophotography...
Always remember to take off the mask BEFORE doing your real exposure... 
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Chris Vedeler
Astro-Physics 160EDF
Astro-Physics 900GTO
Q453HR / QHY8 CCD camera
Canon 450XSi
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www.aznightsky.com
Scottsdale, AZ
Edited by cvedeler (09/17/08 12:42 AM)
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cvedeler
Carpal Tunnel
Reged: 12/20/05
Posts: 2124
Loc: Scottsdale, AZ
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This is better...
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Chris Vedeler
Astro-Physics 160EDF
Astro-Physics 900GTO
Q453HR / QHY8 CCD camera
Canon 450XSi
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www.aznightsky.com
Scottsdale, AZ
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Snow dog
Carpal Tunnel
Reged: 07/17/05
Posts: 1770
Loc: Alberta Canada
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Quote:
How to not do astrophotography...
Always remember to take off the mask BEFORE doing your real exposure...
Hmmmmm. I don't know. Are you sure you did not capture a squadrod of Imperial fighters that forgot to turn off the navigation lights before invading?
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Marc
Someone get these crazy dogs off me
12" LX200 Classic
ETX-90PE
Meade DSI
Canon AE-1, EOS Rebel 350
My Home Page
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jsmiller58
sage
Reged: 06/19/06
Posts: 240
Loc: Out there, Way out there
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Look on the bright side - from all appearances, it would have been a great photo as you managed to achieve fantastic focus across the FOV...
James
Quote:
How to not do astrophotography...
Always remember to take off the mask BEFORE doing your real exposure...
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- 90mm WO refractor
- 11" Orion SCT
- PlaneWave CDK17 ("Cosmic Cannon")
- MallinCam Hyper Color Plus
- More eyepieces than I can use, but not one Ethos... Hmmm... Where's the economic recovery?
- Atlas EQ-G mount
- Losmandy GM-8 mount
- AP 1200GTO mount
- Pro-Dome-15 Obs
- A wife who doesn't understand my fascination with faint fuzzies, but encourages me anyway
- A 17 year old son who calls me just another nut job with an observatory
- A 15 year old son that still thinks I am cool
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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BTW One can use the mask to correct focal plane tilt. Just take a picture of bright stars in each corner and you know which corner needs adjusting in what direction. And if you can add dial indicator to the focuser you may measure exact values. (That's what I plan to do soon).
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Jerry3672
Vendor - Quantum Astronomy Products
Reged: 01/20/08
Posts: 498
Loc: Lexington NC
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Quote:
How to not do astrophotography...
Always remember to take off the mask BEFORE doing your real exposure...
You are not alone in this.
http://apod.nasa.gov/apod/ap971119.html
November 1997. NASA had diffraction spikes on an Image of M8
Just how big of a Bahtinov mask does the Hubble take??? 
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Meade LXD75-SN-8, SN-10, C11
DSI Pro
Canon XSi 450D unmod
www.spike-a.com Bahtinov Style Focus Mask
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Jerry3672
Vendor - Quantum Astronomy Products
Reged: 01/20/08
Posts: 498
Loc: Lexington NC
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Quote:
BTW One can use the mask to correct focal plane tilt. Just take a picture of bright stars in each corner and you know which corner needs adjusting in what direction. And if you can add dial indicator to the focuser you may measure exact values. (That's what I plan to do soon).
Very good Idea Dennis. I hope to have clear skys soon and work on a method to collimate with the Bahtinov mask.
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Meade LXD75-SN-8, SN-10, C11
DSI Pro
Canon XSi 450D unmod
www.spike-a.com Bahtinov Style Focus Mask
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Nocturnal
Pooh-Bah
Reged: 09/14/05
Posts: 1004
Loc: CT, USA
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Quote:
Quote:
BTW One can use the mask to correct focal plane tilt. Just take a picture of bright stars in each corner and you know which corner needs adjusting in what direction. And if you can add dial indicator to the focuser you may measure exact values. (That's what I plan to do soon).
Very good Idea Dennis. I hope to have clear skys soon and work on a method to collimate with the Bahtinov mask.
I can see how Dennis' idea would work (and it's a great idea!) but not yet how the mask would help with collimation. Collimation is a pain so any help there would be much appreciated!
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Best,
Sander
C11-HyperStar on Atlas EQ-Q driven by EQMOD
William Optics M110 With FR-III/TRF-2008
DS2090 guide scope
QHY-8, DSI-Pro and DSI cameras
watec 802h video camera with KIWI OSD
Astro stuff: http://www.tungstentech.com
My Astro Photos
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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In my case SN10+MPCC when I collimate with CCDInspector the focal plane is severely tilt. So my idea was to collimate with CCDInspector, then use Bahtinov mas to collimate the focuser, then use CCDInspector again with non tilted focal plane.
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Jerry3672
Vendor - Quantum Astronomy Products
Reged: 01/20/08
Posts: 498
Loc: Lexington NC
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Nocturnal- This is just an idea I have after testing several Bahtinov masks on different scopes. One was way out of collimation and had a very poor diffraction spike pattern. Blur! but I didn't see if the blur could be used in some way to do a final collimation. The scope we were testing was collimated with a laser, and then we had a very nice clean diffraction spike pattern.
So my theory is if the pattern can be seen with a scope that has poor collimation, the maybe the Bahtinov mask could be used to help Collimate.
Dennis and I exchanged ideas on another thread about a Collimation method for a SN scope, so I'm sure with the help of this group here we can come up with some good tests.
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Meade LXD75-SN-8, SN-10, C11
DSI Pro
Canon XSi 450D unmod
www.spike-a.com Bahtinov Style Focus Mask
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Nocturnal
Pooh-Bah
Reged: 09/14/05
Posts: 1004
Loc: CT, USA
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Great! It would be wonderful if this proves to be a reliable collimation tool.
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Best,
Sander
C11-HyperStar on Atlas EQ-Q driven by EQMOD
William Optics M110 With FR-III/TRF-2008
DS2090 guide scope
QHY-8, DSI-Pro and DSI cameras
watec 802h video camera with KIWI OSD
Astro stuff: http://www.tungstentech.com
My Astro Photos
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John Wunderlin
Vendor - Spike-a Focusing Mask
Reged: 10/01/04
Posts: 655
Loc: Mineral Point, Wi
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Quote:
How to not do astrophotography...
Always remember to take off the mask BEFORE doing your real exposure...
I've got a couple of images that look just like that 
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John Wunderlin
Vendor - Spike-a Bahtinov Focusing Mask
Empire Ranch Observatory
Iowa County Astronomers
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Mike I. Jones
Carpal Tunnel
Reged: 07/02/06
Posts: 1533
Loc: Fort Worth TX
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The Bahtinov pattern in post 2626350 above is THE right way to do these masks, for the following reasons:
1. You want an even number of open slats either side of the horizontal centerline. This allows the opaque slat to be on centerline, letting you rotate the mask to hide the vanes on a 4-vane spider.
2. Putting the central obstruction on the Bahtinov mask is redundant and in fact could introduce scattering errors; the Newtonian diagonal or Cassegrain secondary provides the exact obstruction. No reason to double-book the CO. Including the CO on the Bahtinov also creates unnecessary scaling difficulties.
3. I also see masks here that are blacking out the triangle between the diagonal lines. This unnecessarily costs brightness at the image. Leave the diagonal slats open right to their intersection with the horizontal crossbar.
4. The mask design in post 2626350 has no scaling issues. Generate a unity diameter set of X,Y coordinates, then scale it to any aperture desired and cut away.
Not sure about the tennis racket/nylon string idea. The Bahtinov requires an asymmetric aperture to get the central spike to translate through focus. If the nylon strings go all the way across the pupil, the translation of the central spike relative to the X spikes is lost. You get the Bahtinov diffraction pattern, but not the center spike translation. The spikes just get wider as you rack either side of focus.
Dennis, thanks for bringing this to the world's attention. Mr. Bahtinov, if you read this or can get someone to translate for you, GOOD IDEA, MAN!
Mike
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56 mirrors, lenses, 16" f/6 Newt, 6" f/10 refractor, TOA-130S, Tinsley 5" f/15 Mak, 6" f/4 RFT, Coronado PST. Still to build: 24" f/10 Modified Dall-Kirkham, 10" f/26 Mak, 8" f/12 apo, spectrohelioscope, Herrig, Schupmann, and others.
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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Ok, let me explain the "central obstruction" part. If you look at my picture it's not an obstruction, it's a hole in which my secondary mirror holder goes. This way the whole mask is secured to the secondary mirror holder. It was my only purpose and it works nicely. Of course there's no point in making black obstructed part.
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Mike I. Jones
Carpal Tunnel
Reged: 07/02/06
Posts: 1533
Loc: Fort Worth TX
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Yep, I understand. It's probably a nit, but if the spider is offset on a Newtonian to properly decenter the diagonal, that's going to offset the Bahtinov as well, if it's mounted on the secondary stem. This slight offset won't interfere with the Bahtinov diffraction behavior, but the mask may be offset relative to the tube ID and cause mechanical interference. The folks I've discussed this with so far are just going to center and mount the masks directly on the end of the Newtonian tube and not on the secondary stem.
Of course this decentering doesn't apply to a refractor, Cassegrain or Gregorian. Again, the mask in post 2626350 is the best design, as it serves both obstructed and unobstructed pupils equally well.
Mike
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56 mirrors, lenses, 16" f/6 Newt, 6" f/10 refractor, TOA-130S, Tinsley 5" f/15 Mak, 6" f/4 RFT, Coronado PST. Still to build: 24" f/10 Modified Dall-Kirkham, 10" f/26 Mak, 8" f/12 apo, spectrohelioscope, Herrig, Schupmann, and others.
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