Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1297
Loc: Kiev, Ukraine
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In my SN the offset is implemented by gluing the mirror off-center, while the holder is still centered.
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jgraham
Postmaster
Reged: 12/02/04
Posts: 6688
Loc: Dayton, Ohio
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I suspect the design is fairly forgiving. I think my first mask violated just about all of these guidelines and it works like a champ. My second was a lot cleaner, though I haven't had a chance to test it yet.
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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
Rebel XT/XTi, DSI Pro (I, II, & III), DSI, LPI, Electronic Eyepiece, Phillips SPC900NC
Tasco 60mm Refractors
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cvedeler
Carpal Tunnel
Reged: 12/20/05
Posts: 2118
Loc: Scottsdale, AZ
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I agree with John, the design is very forgiving. I too violated pretty much everything on my first mask (reflector mask on a refractor, lines about twice as wide as they were supposed to be and even a Popsicle stick blocking the central opening!) but it worked good enough to find perfect focus in about 10 seconds.
My latest generation mask from Davids mask generator software, that should be optimized exactly for my scope only produces slightly sharper defraction lines and I am able to resolve the inner pattern next to the center. How critical is this? While it may look nicer, it makes little difference in practice as perfect focus is achieved either way.
The mask is not a scientific instrument that must be optimized to close tolerances. If you take any of the posted images of the mask on this tread, size it for your scope, cut out the pattern with left-handed kiddie scissors and your mask will work well enough to focus perfectly.
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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 03:20 PM)
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Joe F Gafford
professor emeritus
Reged: 12/15/06
Posts: 508
Loc: Denver, Colorado, US
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Here is a mask I made for the 18". I tested this last night and seems to work. Stereo glasses needed for this image. Joe.
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JMI 18" f4.5 Newtonian, split ring mount
10" f4.5 Newtonian on GEM (was a DS-10 once upon a time)
50 and 110 mm Mamiya RZ lenses with homemade adapter
ST-2000XM camera
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raf1
super member
Reged: 11/18/05
Posts: 136
Loc: Texas
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Chris makes an interesting observation. On my original mask (bottom right) which Adam generously provided to the forum, there are 15 horizontal cuts of ~5mm width for my TEC160. This worked very well for me on first light - excellent focus and easy to see the center defraction spike move in and out of focus. Then David went over the top with his excellent mask generator so I created another mask for the 160 using that. Now, I'm the first to admit that I probably porked some of the data entries into the mask generator but the final product is different from Adams scalable mask. The generated mask has 11 horizontal cuts of ~8mm width which would allow slightly more light through the mask. The idea here is to get the best focus tool with the fewest number of cuts in the mask (I need to also create 80 and 100mm refractor masks). I've attached images of the two masks for comparison and I'll report back after comparing the two in my next imaging session.
Cheers and clears.
Ron
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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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Nice, I look forward to hearing your report Ron. My scalable drawing was originally designed for my 12" scope so that is the reason for more lines I think. I was lazy and didn't want to make a new mask for every possible focal length and aperture. That’s why I am very grateful to David for his generator! 
Joe - I am going to hunt you down at Okie-Tex so I can see how that mask works on your Dob... OK - what I really mean to say is I want to look through your Dob please. 
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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Jason Irby
super member
Reged: 07/22/07
Posts: 197
Loc: Texas
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Quote:
Here is a mask I made for the 18". I tested this last night and seems to work. Stereo glasses needed for this image. Joe.
Man, thats a heck of a short focal length on that 18" dob!
Either that or you are about to grill some brauts!
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Clear Skies,
Jason Irby
http://jasonirby.net/astronomy
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jimguy08
member
Reged: 07/17/08
Posts: 17
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One Bahitnov mask for two refractors:
I used one of Adam's efforts, played around with it, and sent a PDF file off to http://www.customlasercutting.com/ For $70 they did a 1/4 inch thick ABS plastic rendition.
I glued two birch plywood disks (found in the craft section of a Wal Mart) together. I then used hole saws to cut.
The interior circle, cut all the way through, fits the OD of the dew shield on an Orion 80ED and the "grove" that you can see cut outside of this circle fits the OD of the dew shield on a Celestron C102F refractor.
All works fantastically, very nice diffraction spikes on both scopes.
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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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jimguy08
member
Reged: 07/17/08
Posts: 17
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Flip side of the "One mask for two refractors":
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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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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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Great solution Jim! A two-for-one deal with a little elbow grease and, voilà!, a sweet little looking tool!
Nice work!
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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raf1
super member
Reged: 11/18/05
Posts: 136
Loc: Texas
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Good job Jim - that's a really neat solution. Maybe I can get away with that on two of my small refractors.
Ron
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-Ron
****************************
Too much "stuff" and too little time to use it .....
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dvmak
member
Reged: 05/11/06
Posts: 90
Loc: Moscow, Russia
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Just to show the masks that we have just received from a local laser cutting workshop.
Masks were created by mask generator mentioned here previously, then they were converted to the vector format that traces the cutting path, as generator produces the masks with the central path for each stripe.
Masks were cut of 3mm thick PMMA black plastic, 2 big masks are for TAL-250K, 250mm F/8.5 catadioptric scope, one smaller mask with denser lines is for 500mm Rubinar-500/5.6 lens and the last one is for 114mm F/10.5 hand made Houghton scope. I shall use one mask for TAL-250K, and the other masks are for my friends.
One of them has already tested it on 114mm F/10.5 scope, the method is sensitive up to 0.05mm refocusing that corresponds to the sensitivity of lambda/10 for this F/number. Good result, I think...
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Clear skies for all!
Dmitry Makolkin
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Elliot
super member
Reged: 09/12/06
Posts: 123
Loc: Medford NJ
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Dimitry - Awesome work! How much did you spend?
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Celestron CPC 1100
APT Wedge
Celestron ED80 GuideScope
SkyShed
SBIG ST9XE
Celestron Ultima 2000
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jgraham
Postmaster
Reged: 12/02/04
Posts: 6688
Loc: Dayton, Ohio
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Very nice! Cutting a Bahtinov mask by hand is a fair amount of work, but worth it. The laser-cut masks look great!
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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
Rebel XT/XTi, DSI Pro (I, II, & III), DSI, LPI, Electronic Eyepiece, Phillips SPC900NC
Tasco 60mm Refractors
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isramirez
Pooh-Bah
Reged: 11/04/05
Posts: 1391
Loc: Mexico City
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Fantastic Masks Dmitry!
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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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dvmak
member
Reged: 05/11/06
Posts: 90
Loc: Moscow, Russia
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The total price for these 4 masks was 1300 RUR, it is about 52 USD.
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Clear skies for all!
Dmitry Makolkin
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blueman
Vendor Blue Sky Accessories
Reged: 07/20/07
Posts: 1347
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Wow, if only we could get such good prices here in the USA!
I need to talk with the local plastic shop to see how much they would charge I guess.
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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Dennis Sakva
Pooh-Bah
Reged: 10/19/04
Posts: 1297
Loc: Kiev, Ukraine
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It's much cheaper to order several masks at once as companies charge a fixed rate to setup the equipment and then some amount per cut length.
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bobblack
member
Reged: 03/30/07
Posts: 39
Loc: Midland,Ontario,Canada
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If I may be allowed to offer a solution for mounting the mask. My wite does crochet needle work and uses these wooden 1/2" hoops. They are available from 4" D up to 20" diameter and are adjustable. They are avaILABLE AT HOBBY STORES AND KNITTING SUPPLIERS.for a couple of bucks.
I just fit mine to the outside of the telescope and glued the mask to the front of it. This will keep it from moving around or falling off. Hope this works for you too, bob
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MartyT
professor emeritus
Reged: 09/28/07
Posts: 682
Loc: Kansas City
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I'm always late to the party.. Didn't hear about this thread until last Friday afternoon, too late to get a Bahtinov mask made before my trip to the club dark sky site on Friday.
But I came home for a while on Saturday and hacked a mask for my C-11, using a big plastic "For Rent" sign from the local hardware store.
The template for the mask came from David's web site, and I imported the SVG into Adobe Illustrator 10. Unfortunately, the SVG is not scaled correctly when I load it with Illustrator - it was about 13.5" diameter instead of the 280mm (11") I requested in the generator. So I drew a 11" long line and scaled the SVG down until it looked about right. I used Illustrator's ability to "tile" the image into multiple sheets when I printed, then taped the individual sheets together and started hacking with the X-acto.
Total cost: $3.49 for the sign, $.10 for the bandages after giving myself a huge blister from using the X-acto knife for 2 hours...
I took it back to the dark sky site on Saturday night and showed it off - nobody there had heard of it, but everyone (myself included) was throughly impressed with how well it worked. I used it both visually and with the DSLR and found it incredibly intuitive.
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Celestron CGE / C-11 (CGE-1100)
Megrez 90 FD APO / 0.8x FR/FF vIII
QHY8, 350D, DSI Pro, SPC900NC
KWIQ Guider (QHY5)
ETX-125AT
12" Lightbridge
My Astrophoto Gallery
Astronomical Society of Kansas City
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