Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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The best focusing device EVER invented!
Let me first say that this device was invented by a respected Russian astrophotographer Pavel Bahtinov. His web page is http://astrophoto.chat.ru/ but it’s rather outdated. I believe he didn’t update it since 2002.
Most of you have probably heard about (or used) Hartmann mask (http://cometman.com/Mask.html). It’s a whole aperture mask with 2-3 holes (triangular or round) that is supposed to facilitate focusing. Frankly, I always found these mask close to useless, as when 3 stars come close to each other it’s almost impossible to tell if you are before focal point, after or right in it.
Pavel’s invention looks like so:
Edited by Dennis Sakva (07/27/08 03:41 PM)
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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When you put this mask over scope’s entrance it introduces very special diffraction spikes much like those produced by Newtonian spider vanes. How they are useful for focusing? One picture worth thousand of words. See yourself. Pay special attention to central spike.
Intrafocal
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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FOCUS!
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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Extrafocal
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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The difference in focuser position between these three pictures is very small, a few tenth of a mm. The method is incredibly sensitive. And much faster than FHWM, or anything else I know (yeah, autofocusing also). It also works for visual! You don’t need to guess if you focused well (when air is unstable) just put the mask and everything is absolutely clear. You have to try to believe. It works for different scope sizes and focal ratios. The general rule to holes’ width is f/s=150-200, where f – is focal length, s is hole step size. So for telescope with 1500mm focal length the step size is 1500/150=10mm (5mm hole, 5mm for uncut space). If holes become too small the formula becomes 3f/s=150-200. eg for 800mm scope you need to cut 2400/s=200 s=2400/200=12mm (6mm cut +6mm uncut).
The angled cuts are placed at 40 degrees to each other.
I cut mine at laser engravement services for $30.
Edited by Dennis Sakva (07/27/08 03:42 PM)
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AlanT
sage
Reged: 08/20/07
Posts: 464
Loc: 122º36' W, 47º37' N, WA USA
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Looks really useful.
What's the mask look like? I poked around the website, but didn't find it.
al
Ahhhh.... now I see. Thanks.
--------------------
Meade 80mm APO
Celestron 6" SCT
CGE, GM-8, & CG-5 GT
ST-2000xcm, DSI Pro II, DSI Pro
( www.alberts-astro.com/astro )
Edited by AlanT (07/27/08 03:50 PM)
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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Sorry, I didn't add the picture when I was entering the post. It's there now.
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DJMcCrady
Carpal Tunnel
Reged: 06/27/03
Posts: 1692
Loc: Seattle, WA
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Impressive!
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++don;
http://starryvistas.net
Tak Sky 90, Tak EM200, STL-4020M
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MtnGoat
Pooh-Bah
Reged: 02/18/07
Posts: 1206
Loc: Columbia Gorge, WA
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Nice! I've got to make one of these. I'm hoping keeping the ratios about the same will do the trick.
I've been experimenting with different shapes myself, and wondering about other ways of using the diffraction properties and intra/extra focus effects to best advantage, that looks like a very intelligent way to do so.
My fav mask now consist of two slits at right angles to each other.
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"Ignorant people think it's the noise which fighting cats make that is so aggravating, but it ain't so; it's the sickening grammar they use." Mark Twain
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MtnGoat
Pooh-Bah
Reged: 02/18/07
Posts: 1206
Loc: Columbia Gorge, WA
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Been trying to find the page on his site with the mask details...can't read Russian. Boy, Russian uses a lot of long words! Can't read them of course, but I am struck by how many characters the average word appears to have.
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"Ignorant people think it's the noise which fighting cats make that is so aggravating, but it ain't so; it's the sickening grammar they use." Mark Twain
Edited by MtnGoat (07/28/08 01:11 PM)
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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Pavel didn't post any details on mask on his web-page. He posted it on www.astronomy.ru/forum But that one uses even more looong words  (You didn't study German, do you?)
If you have any questions on mask - please ask. I'll be glad to help.
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imjeffp
Aluminum Falcon
Reged: 09/30/03
Posts: 4891
Loc: Cedar Park, Texas
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>(You didn't study German, do you?)
Yeah, speaking of long words!
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Freddy WILLEMS
Carpal Tunnel
Reged: 11/13/05
Posts: 2523
Loc: Hawaii, Honolulu
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Can you post the link directly to the mask ?
Freddy
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Freddy
Meade 14" LX200 GPS UHTC GPS on permanent pier
Celestron C 14" Peltier cooled for planetary imaging.
Meade 10" LX200 & TITAN 50:1 mount Gemini 'go to'
Meade 127 mm f/9 APO & TITAN 50:1 mount Gemini 'go to'
W/O 102 mm f/7 APO doublet
Orion 80 mm f/7 ED
DFK 21AU04.AS
ToUcam 840 II pro
Canon 10D Unmoddified
Canon 40D Hutech moddified
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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Here is the discussion
http://www.astronomy.ru/forum/index.php/topic,10421.msg244210.html#msg244210
The thread is long and there are several different masks. The one I showed in the first post seems to work the best.
But a few people speak Russian, so If you have questions, do not hesitate to ask. If my descriprion of how to make the mask for specific scope is not clear, please tell, I'll try to rephrase it
Edited by Dennis Sakva (07/29/08 09:40 AM)
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astroandy
Carpel Tunnel
Reged: 06/07/06
Posts: 169
Loc: Hong Kong
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Hi Dennies,
Thank you for the useful information.
I note that there's a line running across the aperture, but it is not exactly centered. How much off center should it be? Does it have any effect if I cut it dead center; and most importantly, what software did you use to draw the layout accurately?
CS,
Andy
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FSQ106ED
Zenith Star 70mm APO
Meade sc8
LS60THa-DS FT
EM200 Temma II Jr
Pier Tech 2
ATIK16-HR
ATIK-EFW
Astrodon 9nm Ha, SII; Baader 8.5nm OIII; Meade LRGB, LPS-P2 1.25"
QHY5
DMK21
DBK21
ToUCam Pro II mod.
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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The line is supposed to be centered. But in my case it has no effect on final image. I didn't draw the mask, the guy at laser cutting services used their software. I believe any vector graphics pacage (like Open Office Draw, AutoCAD, etc.) will work.
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Gluon
member
Reged: 02/16/06
Posts: 43
Loc: Austria
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Dennis,
looks really great! Thanks for telling us!
What's the angle of the oblique bars in the left two quarters of the mask?
-martin.
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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You have to try it to belive how helpful it is. Checking focus in the middle of the exposure takes 1 minute
The angle between the bars is 40 degrees.
The mask is quite forgiving to bar width, angles, etc.
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lukasik
Pooh-Bah
Reged: 10/11/05
Posts: 1048
Loc: Lawrenceville, Georgia
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Hi Dennis,
Thanks for posting this info. I'm having difficulty following the link here - I get to the main forum page, but can't seem to figure it out from there since I don't know the language. Do you (or anyone else) possibly have a link to a line drawing I could scale and play with?
Thanks for any help.
Best regards,
Bob
Quote:
Here is the discussion
http://www.astronomy.ru/forum/index.php/topic,10421.msg244210.html#msg244210
The thread is long and there are several different masks. The one I showed in the first post seems to work the best.
But a few people speak Russian, so If you have questions, do not hesitate to ask. If my descriprion of how to make the mask for specific scope is not clear, please tell, I'll try to rephrase it
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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The problem is that you can't easily scale them. Masks are designed to work at a spacific focal length so you can't easily scale mask for 80mm/600mm telescope to 120mm/600mm scope. There were several files I'll post links to them.
Here is the link to 200/F8 telescope by Pavel
http://www.astronomy.ru/forum/index.php?action=dlattach;topic=10421.0;attach=57433
Edited by Dennis Sakva (07/29/08 09:45 AM)
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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Bob, seems like the link was truncated by cloudynights forum engine. I replaced it. Try again.
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lukasik
Pooh-Bah
Reged: 10/11/05
Posts: 1048
Loc: Lawrenceville, Georgia
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Thank you so much for the links Dennis.
Regards,
Bob
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roestman
super member
Reged: 12/18/06
Posts: 128
Loc: Houston Texas
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seems very interesting. for everybodys info, you can go to google language tools and translate the page to english or what ever you speak. not allways correct but it can get you through.
http://www.google.com/language_tools?hl=en
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Rick
TAK TOA-150
12.5" RCOS Truss
C9.25 f/10
WO Zenithstar 110
WO Zenithstar 80
SBIG ST-2000XM CFW-9 w/ Astrodons
FLI PDF focuser
OPTEC TCF-S
AO-8
Canon XTI
Takahashi EM-200
Paramount ME
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idahoman
sage
Reged: 11/25/05
Posts: 473
Loc: Idaho, USA
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This is interesting. But, the files are for CorelDraw, which I do not have. Does anyone have them in a different format? And, how do you scale them for different focal lengths?
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A Guy In Idaho
43° 31' N 112° 4' W
4780 ft elevation
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MtnGoat
Pooh-Bah
Reged: 02/18/07
Posts: 1206
Loc: Columbia Gorge, WA
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he posted the ratios on page on, Idahoman
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"Ignorant people think it's the noise which fighting cats make that is so aggravating, but it ain't so; it's the sickening grammar they use." Mark Twain
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cnstarz
professor emeritus
Reged: 12/22/07
Posts: 549
Loc: Kentucky, USA
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Dennis,
I like this focusing mask thanks for the links and info. I'll try to make one like you've pictured, but first I may use the diffraction angles you've given on a mask like this...LINK
I've been experimenting with the three holed Hartman mask and I think breaking up the symmetry with diffraction spikes like you've described will make it more useful.
Regards,
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Matt
Apogee 50mm BB scope
ETX-60 BB
Meade 70-az
5" DIY Newt (wip)
C6-N on CG-4 GEM
Gallery
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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Hi Matt,
The main advantage of the mask proposed by Pavel is that you see very clearly where are you right now (before focal point, after it) and there two diffraction spikes give nice and easy reference to compare to. The mask at your link provides no such "reference" lines. The picture just gets messy when not in focus. But one thing for sure it's much easier to make and to try.
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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The are a few free vector based graphic software.
http://www.inkscape.org/download/?lang=en
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cnstarz
professor emeritus
Reged: 12/22/07
Posts: 549
Loc: Kentucky, USA
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Dennis,
I understand your point, I'll give it a try. I see the key to this is to have two elements that are complementary and a third that contrasts Like here ... MASK
And as your pictures show, the ability to gauge in and out focus is enhanced by the diffraction spikes. I've experienced some frustration using just the three circle mask so I'm eager to try this novel design.
Thanks 
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Matt
Apogee 50mm BB scope
ETX-60 BB
Meade 70-az
5" DIY Newt (wip)
C6-N on CG-4 GEM
Gallery
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Jerry3672
Vendor - Quantum Astronomy Products
Reged: 01/20/08
Posts: 498
Loc: Lexington NC
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Dennis, I followed your link to Pavels design. I drew up a DXF file in Pro-E and cut this out on a water jet. I made the mask out of Aluminum and just painted it black. I will test this as soon as the clouds break.
Thanks for passing on the design.
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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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John Wunderlin
Vendor - Spike-a Focusing Mask
Reged: 10/01/04
Posts: 655
Loc: Mineral Point, Wi
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Can't wait to hear your results. This looks like a potential holy grail of focusing. And a business opportunity for someone with machining tools...
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John Wunderlin
Vendor - Spike-a Bahtinov Focusing Mask
Empire Ranch Observatory
Iowa County Astronomers
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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Wow... Nice! Looks professional Please let me know how it works for you.
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Jerry3672
Vendor - Quantum Astronomy Products
Reged: 01/20/08
Posts: 498
Loc: Lexington NC
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Thanks, I was going for a professional part. 
John- I do have some nice machine tools and engineering software. I'll have to cut Dennis and Pavel in on the action. Couldn't you just see the look on Pavels face when big royalty checks start rolling in? 
I do think I have an understanding of how the design works, and why you can't just scale it for other size scopes.
The axis is centered for the "left" side and has a precise light block of 50%. The "right" side has a 20 degree angle that is centered to blocked area of the left. The right side has a light block of 40%. The axis of the right open area must align to the center of the left blocked area. If it centered, then the spikes you see when in focus will align correctly.
I don't read Russian, so I had to look a photos and calculations that Pavel posted.
If this works like I think, then it will be simple for me to draw this design for any size scope.
darn clouds  
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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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Joe Bruessow
sage
Reged: 05/31/04
Posts: 312
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This looks really cool... but I have not been ambitious enough to download the translating software... I'll wait until one of you geniuses posts this all in English 
Thanks...
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MtnGoat
Pooh-Bah
Reged: 02/18/07
Posts: 1206
Loc: Columbia Gorge, WA
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not sure how much they'll be, but I'll volunteer for a couple. I tried doing one with card board and X acto knife last night...horrible. way too many long fine cuts, then when removing material one cut doesn't go all the way through and tears the solid piece next to it. After fixing four breaks at less than 25% done, I said &&&$*$## it.
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"Ignorant people think it's the noise which fighting cats make that is so aggravating, but it ain't so; it's the sickening grammar they use." Mark Twain
Edited by MtnGoat (07/31/08 07:17 PM)
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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Actually it's important to keep lines straight and free of burrs as those will interfere with diffraction pattern making it blurred. If you don't like cutting you may try gluing strips of something opaque on mask template.
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Jerry3672
Vendor - Quantum Astronomy Products
Reged: 01/20/08
Posts: 498
Loc: Lexington NC
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Not reading Russian made it hard to understand what the sketch was trying to say.
i see now.
My lines are very straight.
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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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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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Yeah, cutting with laser or water-jet gives very nice cuts, working with X-Acto knifes (MtnGoat) is hard
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blueman
Vendor Blue Sky Accessories
Reged: 07/20/07
Posts: 1391
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It is too bad that no one is making these for sale!
Blueman
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14.5" Starmaster with ServoCat and Argo Navis
AT 8" RC
TV NP101 f/5.4 APO Telvue .8 Focal Reducer
WO 80mm f/6 APO Televue .8 focal reducer
SBig ST2000xm with CFW-9 filter wheel
Astrodon Gen2 filters RGBL
Baader HA,O-III, H-Beta, S-II Filters
Losmandy G-11 Gemini Auto-guided
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Jerry3672
Vendor - Quantum Astronomy Products
Reged: 01/20/08
Posts: 498
Loc: Lexington NC
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someone will soon
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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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One test complete.
This blows my hartman mask away.
Here is my test image going from in focus to out of focus in both directions.
This was only a very small movement with the focus knob
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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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John Wunderlin
Vendor - Spike-a Focusing Mask
Reged: 10/01/04
Posts: 655
Loc: Mineral Point, Wi
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Beautiful! Did you have a chance to image using the resulting focus point?
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John Wunderlin
Vendor - Spike-a Bahtinov Focusing Mask
Empire Ranch Observatory
Iowa County Astronomers
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Jerry3672
Vendor - Quantum Astronomy Products
Reged: 01/20/08
Posts: 498
Loc: Lexington NC
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I did image 5 of Jupiter's moons. I need to do some work in Photoshop for the final image. Himalia is a mag 15 and Jupiter is -2.5, so I have subs from .001 to 60 seconds.
I plan on using them in the August Challenge in the beginner imaging thread.
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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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This is the best image I've seen yet to demonstrate a focusing technique. Thanks for posting! I use Nebulosity 2's HFR technique which works very well too. One of the nice things of quantified focusing is that you can chart it to see trends.
How does this mask deal with seeing? Does the central line shift as seeing changes? That would be a terrific benefit of this mask if it's seeing independent.
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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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That's what I currently use as well, but I have to go back and forth many times before I'm comfortable that I've gotten it even close. I usually spend 10-20 minutes messing with focus and by the time I actually image, the focus may have changed! This looks to be a few seconds to lock it exactly. What a time saver! You'd be able to quickly and easily recheck focus between images and scope movement.
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John Wunderlin
Vendor - Spike-a Bahtinov Focusing Mask
Empire Ranch Observatory
Iowa County Astronomers
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Jerry3672
Vendor - Quantum Astronomy Products
Reged: 01/20/08
Posts: 498
Loc: Lexington NC
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Not sure if seeing changes the image. I just used it for the first time last night. I have lots of testing to do.
here is a 60 second exposure of Jupiter. I was attempting to bring in the mag 15 moon Himalia. This was with a Meade DSI Pro. You can see the spikes off of the other moons are equal in all directions. i think the focus was dead on.
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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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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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It works when the seeing is bad too. Seeing will blur the pattern a bit, but you still see where the true focus is. Yesterday it was very windy and the seeing was terrible. Without the mask I wouldn't be able to focus at all. As FHWM was jumping like crazy.
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FoxK
Carpal Tunnel
Reged: 11/07/07
Posts: 2641
Loc: Cape Cod, MA
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I may try to make one..since we got lots of clouds rolling in lol...
I drink ALOT of coffee....seems the plastic covers on the cans can be exacto'd easier than cardboard. Will give it a go
--------------------
Orion 80mm ED Apo Refractor
8" Classic Dob (used as Newtonian on CG5 mount)
Meade 70-AZ-A 70mm Guider using PHD
LS60TCaK/B600/C
CG-5 Advanced GT Mount
Nikon D40x with T-Adaptors
Philips SPC900NC(1/4"ccd)& Quickcam 9000(1/3"CMOS)
Imaging Source DMK 21AU04.AS
- click for cloud prediction for Plymouth, MA. area
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Nocturnal
Pooh-Bah
Reged: 09/14/05
Posts: 1004
Loc: CT, USA
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Ok so that's very interesting indeed to be able to focus through seeing. Thanks!
--------------------
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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MtnGoat
Pooh-Bah
Reged: 02/18/07
Posts: 1206
Loc: Columbia Gorge, WA
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gee, thanks for showing us how good it works. now wanting one is even worse!
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"Ignorant people think it's the noise which fighting cats make that is so aggravating, but it ain't so; it's the sickening grammar they use." Mark Twain
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Wmacky
professor emeritus
Reged: 11/24/07
Posts: 583
Loc: Middleburg Fl US
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If someone doesn't take advantange of this opertunuty, i'm buying a water jet, and setting up shop!
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William
C-11 SCT
EON 80ED
CGE
Canon 40D
Phillips SPC900
SS Autoguider
Scopebuggy
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MtnGoat
Pooh-Bah
Reged: 02/18/07
Posts: 1206
Loc: Columbia Gorge, WA
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Heck, a laser engraver can do fairly thick plastic and I'm sure there's a decent plastic for this kind of thing
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"Ignorant people think it's the noise which fighting cats make that is so aggravating, but it ain't so; it's the sickening grammar they use." Mark Twain
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Jerry3672
Vendor - Quantum Astronomy Products
Reged: 01/20/08
Posts: 498
Loc: Lexington NC
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Here is one formula from Pavel. I don't read Russian, but you'll see the calculus formula is universal.
Dennis- Do you know how fogiving this is? My 200mm aperture F4 scope worked well with a 6.7 mm horizontal slot, and 21.4 degree angle.
--------------------
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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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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Jerry, the mask is very forgiving to both cut's size and angle between cuts. But the sizes determined by Pavel work really good for CCD chips with 7.4um pixels or close to that (DSLRs).
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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:
It is too bad that no one is making these for sale!
Blueman
Hopefully this isn't bad form... I've requested my status to be changed as a vendor, but I can't wait to share this. I officially unveiled the Spike-a mask at the Iowa Star Party this weekend.
Spike-a Focusing Mask
It took a few weeks to get the manufacturing kinks worked out, legal pieces in place, etc, but we're ready to start selling these now!
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John Wunderlin
Vendor - Spike-a Bahtinov Focusing Mask
Empire Ranch Observatory
Iowa County Astronomers
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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Did you contact Pavel Bahtinov - the inventor of this? I see no mention of his name on your page.
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jimguy08
member
Reged: 07/17/08
Posts: 17
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Yes, I too would be interested if Pavel Bahitnov was contacted prior to launching a commercial venture of this sort. He deserves to be mentioned as the originator, yes?
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Celestron C102F Flourite w/Moonlite focuser
Orion 80ED w/Moonlite focuser
Astro-Tech AT66 Guidescope
Atlas EQ-G Bluetooth enabled
Orion SSAG
QHY8
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JAT Observatory
Got Cookies?
Reged: 02/20/05
Posts: 6762
Loc: Eastern PA
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John,
Unless you talked to Pavel I think what you did was while maybe legally OK was ethically wrong, but that is just my opinion.
This is why people shouldn't post ideas without them being patented. As you can see others will take the idea and make money off of someones else's work. Having said that maybe Pavel really wouldn't mind and maybe even hopes that someone will put his idea to good use. If it was me I would have talked to him first.
As a minimum your post should be moved to the vendors forum.
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-Marcus
The problem with free speech is even the stupid have a voice.
http://www.jatobservatory.org
Currently a SV102A, WO 66mm & 10" LX200GPS OTA on a Paramount ME
(these OTAs subject to change without notice)
Edited by JAT Observatory (09/01/08 02:59 PM)
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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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Sorry guys- I'm in new territory here. When lawyers are in the mix, things can get complicated. They told us since this was posted in a public area more than 1 year ago, the information is considered public domain. However, I agree that there should be recognition of the original inventor. I will follow up on this to get it corrected.
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John Wunderlin
Vendor - Spike-a Bahtinov Focusing Mask
Empire Ranch Observatory
Iowa County Astronomers
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Jerry3672
Vendor - Quantum Astronomy Products
Reged: 01/20/08
Posts: 498
Loc: Lexington NC
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I don't think I can comment on this due to the Cloudy nights terms of service and disclosure we all signed up for when becoming a member. I have contacted the Mods and explained that I should be listed as a vendor. If the Mods want to move my comments to the vendor forum, then I'm all for it.
The legal stuff is being handled by a patent attorney. So I can't comment on any of those issues.
Now back to the original idea of the thread that Dennis started. Everyone is welcome to make their own mask based off of the design that Dennis has described.
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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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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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I don't think anyone here is questioning the legality of you making the masks available for sale. And yes, anyone can do it. It's just seem fair that you mention inventor's name and probably share some profits with him.
Just in case.
By no way I'm financially associated with Pavel. I know him only as a very knowledgeable person always willing to help.
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Tomvictor
sage
Reged: 08/09/04
Posts: 491
Loc: N.59.11.47. Norway
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Let me see if I got it right. Can I use the same mask on my FSQ at f/3.6 - f/5 and f/8?
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Tom Victor
http://www.ccd-astrophoto.com/
Takahashi EM-200 - 10" LX200ACF - Artemis 4021M - Mini Borg 60ED - FLI CFW - DSI PRO II. Canon EF200L f/2.8 - 450D - Baader mod. 350D.
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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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I tested the 12" version with an F4.7 XT10 and and F10 LX50-10" - it worked well in both scopes.
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John Wunderlin
Vendor - Spike-a Bahtinov Focusing Mask
Empire Ranch Observatory
Iowa County Astronomers
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Tomvictor
sage
Reged: 08/09/04
Posts: 491
Loc: N.59.11.47. Norway
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Thanks John.
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Tom Victor
http://www.ccd-astrophoto.com/
Takahashi EM-200 - 10" LX200ACF - Artemis 4021M - Mini Borg 60ED - FLI CFW - DSI PRO II. Canon EF200L f/2.8 - 450D - Baader mod. 350D.
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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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Dennis,
What did you make your mask out of? $150 ++ is a little steep for me so I am going to make my own.
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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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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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I didn't do it by myself. I ordered one at local shop that specializes on advertisement materials. They sell lots of self gluing films, light boxes, etc. They also offer laser cutting services. The 10" one made of 3mm acrylic cost me around $30 to cut. You can also cut one from thick plastic sheet with x-acto knife, but that's not very easy. Though my friend cut 150mm one without too much trouble (he is very diligent). You can also glue black stripes of paper over the mask instead of cutting them.
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Tomal
member
Reged: 03/24/08
Posts: 95
Loc: Norway
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Adam, how do you plan to make this mask ?
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Celestron C8 203mm f/10
Meade 5000 series APO 80mm f/6
Sky-Watcher Newtonian 203mm f/5.9
Sky-Watcher Maksutov-Cassegrain 80mm f/12,5
Sky-Watcher Finder/Guide scope 50mm f/4
CG-5 GT
Canon 40D (Unmod)
SSAG
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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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Thanks Dennis for the info. I'll call around to some of our local shops to see if they also offer this service. Otherwise I'll look into making my own out of a sturdy plastic.
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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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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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I downloaded the InkScape opensource software Dennis had mentioned and worked my way through how to use it. I finally came up with this design.
I have calls out to various laser cutters in town for quotes. I will most likely go with a black opaque acrylic rather than aluminum unless I can find a place that has the anodized. I don't want to be placing spray painted surfaces next to my optics. My size is for the 12" SCT so the slats are 10mm wide and spaced 10mm. The central obstruction is 10cm and the entire diameter for the full disc is 35cm.
I really like the way it turned out and can't wait to try it out!
I named it the Pavel Mask.. I thought it was a fitting name.
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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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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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I just placed an order with a local company that will cut it out of a 3mm black opaque acrylic for me for $37. I think I will bond a couple of acrylic "hangers" on it so it will not fall off.
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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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Jerry3672
Vendor - Quantum Astronomy Products
Reged: 01/20/08
Posts: 498
Loc: Lexington NC
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Nice Drawing Adam. That looks like it will work just fine.
With your 12" LX200 and a DSI pro you should be able to focus on a Mag 6 or 7 star with no problem.
Keep us posted on how it works.
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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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mikefulb
super member
Reged: 04/17/06
Posts: 167
Loc: Central NC
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Saw this article the other day and I had to try it out. I went low tech and cut out a mask from some heavy felt-like material I found at a craft store and built a simple wooden frame. Going to try it out tonight!
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Michael Fulbright
http://msfastro.net
Edited by mikefulb (09/02/08 07:46 PM)
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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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Nice Michael! Let us know how it works. If I wasn't able to find a place here in Denver that could cut my drawing for my I was going to go that very route.
Good luck mate!
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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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Nocturnal
Pooh-Bah
Reged: 09/14/05
Posts: 1004
Loc: CT, USA
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I would also like to make mine out of flexible material so I'm curious to read how this works for you!
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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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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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I started thining about it a little more and decided to have the shop cut a smaller one for my 80mm scope. I tried just scaling it first and it worked perfectly according to the equation and my particular scopes. I also added a few extra pieces that I can fashion into 'hangers'.
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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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Snow dog
Carpal Tunnel
Reged: 07/17/05
Posts: 1770
Loc: Alberta Canada
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Quote:
I downloaded the InkScape opensource software Dennis had mentioned and worked my way through how to use it. I finally came up with this design.
I have calls out to various laser cutters in town for quotes. I will most likely go with a black opaque acrylic rather than aluminum unless I can find a place that has the anodized. I don't want to be placing spray painted surfaces next to my optics. My size is for the 12" SCT so the slats are 10mm wide and spaced 10mm. The central obstruction is 10cm and the entire diameter for the full disc is 35cm.
I really like the way it turned out and can't wait to try it out!
I named it the Pavel Mask.. I thought it was a fitting name.
I like your design also. What's the angle that the right side slots are cut at? It looks like it's around 35 deg or so. Left side looks like 90. Thanks.
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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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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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Quote:
I like your design also. What's the angle that the right side slots are cut at? It looks like it's around 35 deg or so. Left side looks like 90. Thanks.
Yup, the left side is 90 degrees, the right top side is +20 degrees while the right bottom is -20 degrees.
They will cut tomorrow so I should get them by Friday hopefully.
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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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John Wunderlin
Vendor - Spike-a Focusing Mask
Reged: 10/01/04
Posts: 655
Loc: Mineral Point, Wi
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Looks great. I also tried printing the pattern on a blank transparency, but it seems to be important to have the clear openings. I think the transparency material wasn't optically clear enough.
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John Wunderlin
Vendor - Spike-a Bahtinov Focusing Mask
Empire Ranch Observatory
Iowa County Astronomers
Edited by John Wunderlin (09/02/08 10:43 PM)
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Nocturnal
Pooh-Bah
Reged: 09/14/05
Posts: 1004
Loc: CT, USA
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That's actually a great idea Some overhead sheets for printers are quite matte to make the ink stick. If yours were clear I'm not sure why it wouldn't work with a bright enough star.
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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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mikefulb
super member
Reged: 04/17/06
Posts: 167
Loc: Central NC
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Ok just tested my mask made from thick felt on my Takahashi Epsilon 180ED and it works just awesome. The scope is 500mm and f/2.8 so focusing is always a PITA. I only tried focusing on brighter stars but it was very trivial to get perfect focus. The out of focus images looked very similar to the animation someone posted earlier. I could move the focuser in increments of 3 Robofocus steps (I think that corresponds to 1/1200 of a turn of the focus shaft) and see distinct changes in the diffraction pattern.
I thought about using a clear transparency sheet and printing the pattern but I was worried the sheet would slightly affect the focus position and so when I removed it then I would still be slightly out of focus. Make sense?
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Michael Fulbright
http://msfastro.net
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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:
That's actually a great idea Some overhead sheets for printers are quite matte to make the ink stick. If yours were clear I'm not sure why it wouldn't work with a bright enough star.
Well, it worked fairly well visually- I could see the triple spike pattern, but it was a little 'wiggly'. When I added the CCD, it was badly distorted and I couldn't really use it. However, I was just holding it in front of the scope by hand- I'll bet if you had a rigid frame it would have worked much better.
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John Wunderlin
Vendor - Spike-a Bahtinov Focusing Mask
Empire Ranch Observatory
Iowa County Astronomers
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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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Quote:
I thought about using a clear transparency sheet and printing the pattern but I was worried the sheet would slightly affect the focus position and so when I removed it then I would still be slightly out of focus. Make sense?
I had thought the same thing. Placing a filter in the light path can cause the focus to go slightly out and I figured a overhead transparency would be quite below par to a filter. With that said though. I bet you could print it out on a clear transparency, cut out the "clear" areas, and mount it into a rigid housing like mentioned above. I think that might fit the bill as long as it doesn't wobble too much in a breeze.
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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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Jerry3672
Vendor - Quantum Astronomy Products
Reged: 01/20/08
Posts: 498
Loc: Lexington NC
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Good job Mike. Great night here in NC Too!!
How did you hold the mask in place?
You could be on to the reason why the clear transparency sheet hasn't worked for others.
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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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mikefulb
super member
Reged: 04/17/06
Posts: 167
Loc: Central NC
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Quote:
Good job Mike. Great night here in NC Too!!
How did you hold the mask in place?
You could be on to the reason why the clear transparency sheet hasn't worked for others.
Yes it is spectacular weather here tonight. I'm at home so I'm doing H-alpha imaging from the suburbs. I hope to get to a dark site tomorrow however.
I just stuck 2 push pins into the wood frame at the right place so I could 'hang' the frame on the scope. If it were windy it might be a problem but I always carry blue painters tape for such occasions!
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Michael Fulbright
http://msfastro.net
Edited by mikefulb (09/03/08 12:09 AM)
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Tomal
member
Reged: 03/24/08
Posts: 95
Loc: Norway
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I just made a mask from some cardboard, it works like a charm, very easy to focus with
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Celestron C8 203mm f/10
Meade 5000 series APO 80mm f/6
Sky-Watcher Newtonian 203mm f/5.9
Sky-Watcher Maksutov-Cassegrain 80mm f/12,5
Sky-Watcher Finder/Guide scope 50mm f/4
CG-5 GT
Canon 40D (Unmod)
SSAG
Edited by Tomal (09/03/08 05:07 PM)
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Nocturnal
Pooh-Bah
Reged: 09/14/05
Posts: 1004
Loc: CT, USA
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I just drew one with Inkscape and printed on regular paper. I hope to try it tonight. After cutting out the gaps of course
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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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groz
Pooh-Bah
Reged: 03/14/07
Posts: 1038
Loc: Duncan, BC
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Quote:
I just drew one with Inkscape and printed on regular paper. I hope to try it tonight. After cutting out the gaps of course
I did one last night for an 80mm, the quick and dirty way. I grabbed the graphic out of an earlier post in this thread, scaled it up to 80mm diameter, and printed it. took the printout, and an exacto, sat out on the back deck for 30 minutes making fine cuts. The idea was, dont worry about a 'perfect' mask, just 'good enough' to take a look and test the concept.
After I had the mask cut, I put the ST-80 (normally used as a guider, but fits the small tripod) on a tripod, pointed at polaris, with a Canon 300D attached. I used the motofocus to make very small focus adjustments (about 1/20 of a second, at the low speed). Not the most precise measurents, but, I know that those kind of button pushes on the motofocus will take around a thousand of them to get a full rotation of the focus knob.
I've done this test in the past with software to measure FWHM and try find focus with this setup. Results vary from sporadic to inconclusive. I've never seen FWHM measurements give a conclusive result with this ST-80 and a dslr, have tried numerous methods.
I have 20 odd jpeg fine shots taken as I walked the camera thru focus in those small increments. There is absolutely no question which one is best focused, and there is absolutely no doubt it is moving between shots.
If I dont get to it tonite, over the weekend, I'm going to take the time to do a better job of cutting, using a strait edge to make the cuts, and do a coffee can lid that fits onto the 127mm mak perfectly. Based on what I saw last night, focussing issues for the DSLR on these telescopes is going to be a thing of the past. I've got an SCT coming next week, and if this works on the mak as well as it did on the little refractor, the mask will be waiting for the SCT when it arrives.
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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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If anyone needs a scaled drawing of the one I made up let me know. I can try it out with your particular focal length and see if it scales properly. Download and install InkScape and you will be able to printout the vector based image and not have to worry about those nasty stair step edges caused from the jpg I posted earlier.
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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isramirez
Pooh-Bah
Reged: 11/04/05
Posts: 1391
Loc: Mexico City
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Quote:
If anyone needs a scaled drawing of the one I made up let me know.
What about for a maksutov with 180mm diameter and 2700mm focal length? it would be possible gentleman?
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Santel MK9 & MK6
IntesMicro 715
Celestron SCT6 & ONIX80 EDF
Meade SN6 & AR6
HiOptic 6in MakCass.Gregory
DBK + DMK + NexImage + LPI
CG-5 & LXD75 Mounts
many EP's, Barlows and Binoviewers
Great astronomic passion 
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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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It is not an 'exact' scale but it is pretty close. Your scope would be 2700/150 or 200 so the slits would be 7-9mm slits 7-9mm apart. My scaled version would put it right about 5mm slits for your 180mm apature. Shot me your email in a PM and I'll email you the scaled version. Remember to download and install InkScape so you can view and print it out.
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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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groz
Pooh-Bah
Reged: 03/14/07
Posts: 1038
Loc: Duncan, BC
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Quote:
If anyone needs a scaled drawing of the one I made up let me know. I can try it out with your particular focal length and see if it scales properly.
Some common sizes that I'm sure a lot of folks will be interested in.
2032mm fl, 200mm diameter (8 inch sct f/10)
1280mm fl, 200mm diameter (8 inch sct with .63 reducer)
4064mm fl, 200mm diameter (8 inch sct, 2x barlow, for planetary stuff)
585mm fl, 80mm diameter (Williams zs80)
1540mm fl, 127mm diameter (orion apex 127)
400mm fl, 80mm diameter (orion st80, common guidescope)
Ok, that covers most of what we have here
But this does bring up the interesting question. Will I still get useable diffraction spikes in all of the 8 inch configurations, from a single mask, or, does it really need the different spacings on different focal lenghts ?
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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:
Will I still get useable diffraction spikes in all of the 8 inch configurations, from a single mask, or, does it really need the different spacings on different focal lenghts ?
I tested our 12" model on both f/4.7 and f/10 10 inch scopes. Although the spike pattern is slightly different, both provided the diffraction spike pattern. Here are 2 rough images I shot for comparison:
f/4.7 scope
f/10 scope
Both provided usable patterns. Note that both of these images were in scopes that weren't currently tracking, so these are very fast exposures and are not as clear as they could be. At the time I just wanted to get the basic tests done.
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John Wunderlin
Vendor - Spike-a Bahtinov Focusing Mask
Empire Ranch Observatory
Iowa County Astronomers
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Jerry3672
Vendor - Quantum Astronomy Products
Reged: 01/20/08
Posts: 498
Loc: Lexington NC
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Big thanks to those in Pavels group for the original concept. If anyone here speaks Russian it sure would be nice to have someone to tell them thanks. I have sent e-mails to Pavel, but I'm afraid my russian translation is rough. I did get his web site translated. he offers a lot of information to the amateur astronomy community in Russia.
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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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Quote:
Both provided usable patterns. Note that both of these images were in scopes that weren't currently tracking, so these are very fast exposures and are not as clear as they could be.
What would you call a 'very fast' exposure? I was using 1/2 second last night in the ST80, and got the bit below. In hindsight, I probably should have let it go a few seconds, allow the star to blow out a bit, and let the diffraction spikes come up better.
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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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Groz, I just tried out a paper cutout for my 80mm scaled down from the original 35cm disc. The pattern was really distinct. I focused on my own first and then placed the mask over to see how close I got. While thought I was right on the diffraction pattern showed I was still off. Sure enough, after refocusing with the mask the image of Jupiter was spot on!
I think for 'optimal' performance the strict equation should be followed but to try it out and build a working model, the scaling should work just fine.
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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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Jerry3672
Vendor - Quantum Astronomy Products
Reged: 01/20/08
Posts: 498
Loc: Lexington NC
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Looks like a lot of this conversation deals with the math to get the correct cutout. The math formula is based off of a mag 0 star. It takes into account the focal ratio, but the bottom line is the light gathering power of the scope is what determines the cutout and not just the focal ratio.
The cut out size is not just a linear graph. so just scaling the 8 inch down for a 80mm scope will need a small tweak. The easy cheat method is just to cut the angled side just a bit bigger to balance the diffraction spikes. so if you have a 4.75 mm slot and 4.75 spacing on the horizontal side, then you should cut 5.25 mm slot and 4.25 spacing on the angled side. This will help balance the spikes.
To answer groz- yes! the same mask will work for all 8 inch scopes. The tweak in cut sizes is only if you want dead perfect diffraction spikes.
--------------------
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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cvedeler
Carpal Tunnel
Reged: 12/20/05
Posts: 2124
Loc: Scottsdale, AZ
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Holy precision focusing Batman!
I think I've just fallen in love. I have never focused so precisely so quickly with my astrophotography in 20 years of doing this hobby.
I went from putting my DSLR on my scope to PERFECT focus in about a minute. This is a test shot of M2 I just took. This is a 30 second unguided exposure, 100% crop. I've got stars down to almost a pixel of my Canon DSLr at 1200mm focal length!
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Chris Vedeler
Astro-Physics 160EDF
Astro-Physics 900GTO
Q453HR / QHY8 CCD camera
Canon 450XSi
----------------------------
www.aznightsky.com
Scottsdale, AZ
Edited by cvedeler (09/04/08 12:08 AM)
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isramirez
Pooh-Bah
Reged: 11/04/05
Posts: 1391
Loc: Mexico City
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Quote:
It is not an 'exact' scale but it is pretty close. Your scope would be 2700/150 or 200 so the slits would be 7-9mm slits 7-9mm apart. My scaled version would put it right about 5mm slits for your 180mm apature. Shot me your email in a PM and I'll email you the scaled version. Remember to download and install InkScape so you can view and print it out.
Got the mail ...i'm praying the rain season finish soon here... thank you so much Pavel
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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A few considerations.
You need to have cuts straight and clean or else additional diffraction effects will wash out the main pattern.
While the mask is quite forgiving to cuts sizes it is still recommended to keep close to those values. The mask is optimized to work on either first or third order spectrums (depending on multiplier). By deviating too much you may have a situation when the first orders spectrum is too tight, while third and consequential orders are too wide for precize focusing.
You may also try experimenting with exposure length. The longer the exposure the higher orders appear.
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nimthor
member
Reged: 02/10/08
Posts: 53
Loc: Durbanville, South Africa
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Hi all!
This is the gratest thread ever!
Few questions ofthings I don't understand.
In the formula f/s=150-200
Firstly I guess this means 150 or 200 or does it mean 150 to 200, so that you can choose any number in between? What does these numbers mean and how do you decide what to use?
The angle is around 40deg to each other for the sloped side, any science behind this angle?
Thanks!
Charles
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Telescopes:
Meade LXD75 SN8, Orion 80mm Guide scope, Celestron 60mm Alt/Az
Camera's:
Pentax K1000, Canon 450D, Canon A700
Binoculars:
Safeway 16x50, Tasco Lumina 10x25
"Never underestimate the predictability of stupidity"
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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150 to 200, so that you don't need to cut exactly 7.34579mm but round to 7 or 8mm (Just a number from my head).
Those are empirically derived numbers. 35-45 will work too, but you'll probably need a bit different cut sizes.
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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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I was reading back over some of the original posts from Dennis and noticed his red mask had a hole cut out in the center.
While Maks, SCTs, and Newts will see no difference I started thinking about refractors. If we were to cut out the center obstruction hole that would allow more light to enter we would be able to focus on dimmer stars. However, I also wonder if the increased central portion of light would start 'washing out' the defraction patterns.
Any thoughts? I think I might try that experiment out at home tongiht with my papaer cutout for the 80 mm and see if there is a big difference.
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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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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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The hole in the center is just for the secondary mirror. For refractor you don't need it. Just continue cuts where the hole is.
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ayiomamitis
super member
Reged: 02/10/07
Posts: 191
Loc: Athens, Greece
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Dennis,
Thanks to both yourself as well as the gentleman who came up with this ingenious creation.
I would like to ask you about the "f/s = 150-200" rule of thumb ... can I assume that it refers to the sum of the slit and the ensuing bar? In other words and using my AP refractor with focal length of 1200 mm, the above rule of thumb yields a value of "s" which is between 6 and 8 mm ... therefore, are the slits one-half of this amount (3-4 mm) and another similar amount for the bar?
As for the angle of the slits for one of the two sides which are not 90 degrees, is this fixed (ex. 20 degrees) or do we have a similar equation for a suggested angle?
Thanks again for your time and attention to this creative tool!
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Clear skies,
Anthony Ayiomamitis
Athens, Greece
http://www.perseus.gr
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Gus_Smedstad
Pooh-Bah
Reged: 07/02/06
Posts: 1108
Loc: Boston 42° 16' N 71° 08' W
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Post #5 makes it fairly clear that you have the numbers correct. A 1200mm focal length gives you a total width S of 6-8mm, so the slits need to be 3-4mm and spaced by the same amount.
I'm not clear at this point whether this is a major improvment over an ordinary Hartman mask which has 6 diffraction spikes. The triangular version gives 18 diffraction spikes, which is really unusable, but if you paint three toothpicks black and attach them to the holes of a 3-circle Hartman mask, you get much the same effect I'm seeing in the animations.
The main difference would seem to be that there are a lot more slits and the specifics of the slit spacing. Perhaps this yields brighter diffraction spikes?
- Gus
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Gus Smedstad image gallery
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Elliot
super member
Reged: 09/12/06
Posts: 123
Loc: Medford NJ
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Hi John - I ordered one from your website today http://www.spike-a.com/# but did not see where it will take 2-4 weeks for deleivery. Why so long? Is that accurate?
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Celestron CPC 1100
APT Wedge
Celestron ED80 GuideScope
SkyShed
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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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Hi- yes, I just added that to the site. The 1st batch of masks I have were prototypes. The 1st production run will be done next week. I'm hoping it will be less than 2 weeks, but I want to manage expectations. If you're interested in a prototype, PM me or email me directly.
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John Wunderlin
Vendor - Spike-a Bahtinov Focusing Mask
Empire Ranch Observatory
Iowa County Astronomers
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Elliot
super member
Reged: 09/12/06
Posts: 123
Loc: Medford NJ
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I will anxiously wait. 
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Celestron CPC 1100
APT Wedge
Celestron ED80 GuideScope
SkyShed
SBIG ST9XE
Celestron Ultima 2000
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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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One additional suggestion for the DIYers, I experimented with wide ribbon of the type you use for wrapping presents. It showed some promise. You could potentially make a 'dreamcatcher' type mask with perhaps a wood slat down the middle and attach ribbon to it in this pattern. I gave up on this path after Jerry & I hooked up.
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John Wunderlin
Vendor - Spike-a Bahtinov Focusing Mask
Empire Ranch Observatory
Iowa County Astronomers
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Gus_Smedstad
Pooh-Bah
Reged: 07/02/06
Posts: 1108
Loc: Boston 42° 16' N 71° 08' W
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As long as you're following this thread, Josh, if you're going to offer these masks, are you going to give any consideration to the slit spacing? I'm unclear how important this is because, not knowing Russian, I haven't read the original thread. But my 8" OTA is an Orion 1000mm, and your site doesn't say whether the slits on an 8" mask are 3mm (for 1000mm f/4.9) or 5-6mm (for a 2000mm f/10).
- Gus
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Gus Smedstad image gallery
Orion Atlas 8 EQ-G
Celestron Onyx 80EDF (guiding / widefields).
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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:
As long as you're following this thread, Josh,
I assume you mean me- John?
Quote:
if you're going to offer these masks, are you going to give any consideration to the slit spacing?
The spacing gets smaller as the diameter of the mask gets smaller. I don't have an 8" with me right now, so Jerry would probably be a better person to ask about that. I suggest PMing him if you want to know the dimensions.
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John Wunderlin
Vendor - Spike-a Bahtinov Focusing Mask
Empire Ranch Observatory
Iowa County Astronomers
Edited by John Wunderlin (09/04/08 11:50 AM)
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Gus_Smedstad
Pooh-Bah
Reged: 07/02/06
Posts: 1108
Loc: Boston 42° 16' N 71° 08' W
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My apologies for the name mistake. For some inexplicable reason I saw "Josh" every time I read "John."
Arrrgh.
- Gus
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Gus Smedstad image gallery
Orion Atlas 8 EQ-G
Celestron Onyx 80EDF (guiding / widefields).
Orion Starshoot Autoguider
QHY8
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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1298
Loc: Kiev, Ukraine
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s=slit+space
So S=10 the cut is 5mm and the uncut space is also 5mm
BUT!
As cuts get too small you can multiply the number by 3 and use 3rd order spectrum (no visual difference) instead of the 1st one. I described all that on 1st page.
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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:
My apologies for the name mistake.
No problem!
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John Wunderlin
Vendor - Spike-a Bahtinov Focusing Mask
Empire Ranch Observatory
Iowa County Astronomers
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Snow dog
Carpal Tunnel
Reged: 07/17/05
Posts: 1770
Loc: Alberta Canada
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Quote:
if you paint three toothpicks black and attach them to the holes of a 3-circle Hartman mask, you get much the same effect I'm seeing in the animations.
Gus
I'm interested in how you put the toothpicks in the holes. I just made a hartman mask for my LX-200 and was going to make one of these but if all I need to do is add a few toothpicks it would be great. Could you post a pic or a sketch of how you did it.
Thanks
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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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John Wunderlin
Vendor - Spike-a Focusing Mask
Reged: 10/01/04
Posts: 655
Loc: Mineral Point, Wi
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Here is a website that describes the process in quite a bit of detail for the Hartmann style.
http://starryvistas.net/Articles/FocusMask/FocusMask.aspx
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John Wunderlin
Vendor - Spike-a Bahtinov Focusing Mask
Empire Ranch Observatory
Iowa County Astronomers
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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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The thing I don't like about the Hartman Mask is I am taking my 12" scope and reducing the light gathering ability down to perhaps 1/5 or more. The triangles produce small diffraction patterns at best and even placing the toothpicks on I saw little difference (in my case).
This Pavel Mask really makes a HUGE distinction on focus by the placement of one spike compared to the other two. I also don't have to worry about zooming in on the star to get a good focus.
Oh, and I get to play with knives and glue to make a new mask!
Bonus all the way around!!! 
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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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Gus_Smedstad
Pooh-Bah
Reged: 07/02/06
Posts: 1108
Loc: Boston 42° 16' N 71° 08' W
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That article on Starry Vistas is where I got the idea for the diffraction toothpicks in the Hartman mask. The circles I used were a lot larger, and I have no trouble picking out the diffraction spikes, though I do typically zoom in with Live View.
More light, brighter spikes, and a clearer relationship between the spikes would be good, though. Eyeballing the focus is a lot better than a plain Hartman mask, but I still sometimes feel I'm guessing whether they're centered, since the intersection is obscured by the star itself.
- Gus
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Gus Smedstad image gallery
Orion Atlas 8 EQ-G
Celestron Onyx 80EDF (guiding / widefields).
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Gus_Smedstad
Pooh-Bah
Reged: 07/02/06
Posts: 1108
Loc: Boston 42° 16' N 71° 08' W
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BTW, we should probably be calling these "Bahtinov Masks", not Pavel Masks. Oh, sure, Pavel rolls off the tongue, but it's sort of like calling something a "Paul Mask."
- Gus
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Gus Smedstad image gallery
Orion Atlas 8 EQ-G
Celestron Onyx 80EDF (guiding / widefields).
Orion Starshoot Autoguider
QHY8
Philips SPC900NC
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xumaxer
sage
Reged: 01/30/06
Posts: 249
Loc: 39º 45' N, 8º 48' W
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Wow! this sure looks promising!
I got one question, though:
- shooting with a WO ZS80FD + 0.8x FR - the focal length on the formula will be the original one (555mm) or with the reducer on (444mm)? will it make a difference?
I also have a 2" extender and DSLR...
BTW, what if I want to get one for my C11?
Thanks!
xumie
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Ciao
xumie
________________________________
C11
FS-102NSV
G-11 Gemini
ST2000XM + CFW10
DMK21AF04.AS
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Gus_Smedstad
Pooh-Bah
Reged: 07/02/06
Posts: 1108
Loc: Boston 42° 16' N 71° 08' W
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I think it's fairly obvious that the final focal length is what matters. Which makes me think that I will need a different mask if I'm using a Powermate to reach 2000mm!
Fortunately for you, the 555mm vs. 444mm difference is well within the margin for error he posted. 3 x FL / (150-200) = 8-11 mm at 555mm, and 7-9mm at 444mm, so 8-9mm will suit either.
- Gus
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Gus Smedstad image gallery
Orion Atlas 8 EQ-G
Celestron Onyx 80EDF (guiding / widefields).
Orion Starshoot Autoguider
QHY8
Philips SPC900NC
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jgraham
Postmaster
Reged: 12/02/04
Posts: 6694
Loc: Dayton, Ohio
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Adam; it took me a while to appreciate the improvement in the light passing through the Bahtinov mask (I like that name) as compared to a Hartman. I also ran into the problem of the classic Hartman loosing sensitivity near the focus and I've been using one of the "+" designs that provides information all the way through the region of best focus like the Bahtinov mask, but it only works well on bright reference stars.
One question about the Bahtinov mask; is it alignment sensitive? In other words, must it be accurately centered to work well? The reason I ask is centering a mask is easy unless you're using a dew shield on a Cat, then it can get tricky.
This looks like a neat design and I'm looking forward to trying it.
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-John
================================================
Homebuilt scopes from 4.25-16.5"
Meade LXD75-N6/SN6/SC8, DSX-90, ETX-60BB, ETX-125PE, DS-2130
Orion StarBlast, BinoViewers, Coronado PST
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Tasco 60mm Refractors
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suburbanskies
sage
Reged: 12/18/04
Posts: 244
Loc: New Jersey, USA
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Yes, recognize the inventor and pay a royalty. It is best for you, despite what is "allowable" within the rules.
Mark
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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:
One question about the Bahtinov mask; is it alignment sensitive?
It does not appear to be. I tested moving the mask's center point around and it did not appear to affect the image significantly. Of course, rotating the mask will rotate the pattern. If it is too far to one side or the other, it may affect the brightness of the affected diffraction spikes, but the center location appears to not change.
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John Wunderlin
Vendor - Spike-a Bahtinov Focusing Mask
Empire Ranch Observatory
Iowa County Astronomers
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Nocturnal
Pooh-Bah
Reged: 09/14/05
Posts: 1004
Loc: CT, USA
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This thing is absolutely AMAZING! I have an F/5.95 110mm refractor with a 0.8x FR. I guestimated the spacing of the mask to be 10mm or 5mm wide slits. Quickly drew one up in the drawing program mentioned above, printed and cut out the slits. I glued the paper mask on a piece of foam board with a hole that turned out to be bigger than the dew shield so the resulting pattern doesn't center. Bam! focus patter is exactly as 'advertised'. Instead of spending 20 minutes with Neb2's HFR focus with numbers jumping all over the place I was focused in about 2 minutes.
My advise: don't worry about the details. Make one from cheap material and try it out.
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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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Tomal
member
Reged: 03/24/08
Posts: 95
Loc: Norway
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Quote:
My advise: don't worry about the details. Make one from cheap material and try it out.
I second that!
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Celestron C8 203mm f/10
Meade 5000 series APO 80mm f/6
Sky-Watcher Newtonian 203mm f/5.9
Sky-Watcher Maksutov-Cassegrain 80mm f/12,5
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CG-5 GT
Canon 40D (Unmod)
SSAG
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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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Wow! What a sensation this little guy is! I wasn't sure what the inventor's last name was so I just stuck with Pavel. However, Bahtinov Mask really is appropriate.
So... The Amazing Bahtinov Mask it is!
Anyway, I just sent out an email to the folk who wanted a scalable drawing I had down on my first design. I modified the drawing to work a little better for a refractor since those scopes do not have the center obstruction to worry about.
I did make a bit of a blunder though. I had asked folks to send me their aperture sizes instead of the full scope opening. oops
In any event I hope you all find even better and more inventive ways to make, cut, paste, tape, glue (oh, maybe not glue), sew, tack, or otherwise adhere your new Bahtinov Masks to your scope.
A HUGE thanks again to Dennis for first introducing us all to this incredible new focusing aid. And of course, we need to heartily thank the inventor of this awesome design and for his generosity at giving this knowledge to us open source!
Thank you Mr. Bahtinov!!!
Here is the refractor modification.
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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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Galaxyhunter
Pooh-Bah
Reged: 01/02/06
Posts: 1227
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