Mark Sibole
Pooh-Bah
Reged: 11/30/07
Posts: 1097
Loc: Fife Lake Mi.
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Thanks Adam,
Ive found focus is almost impossible to miss with the mask.
Mark
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Regards,
Mark Sibole
astronomy.qteaser.com
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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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Hmm, you say 'almost impossible' did you have some issues?
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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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Mark Sibole
Pooh-Bah
Reged: 11/30/07
Posts: 1097
Loc: Fife Lake Mi.
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I never say impossible cause something can always go wrong in this hobby lol.
Lets just say you can reach focus in less than 5 minutes with a 99.8 percent chance of getting perfect focus.
The .2 percent is usually human error.
I used the design for the refractor and it worked great.
Mark
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Regards,
Mark Sibole
astronomy.qteaser.com
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Tomal
member
Reged: 03/24/08
Posts: 95
Loc: Norway
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I nominate this thread for "Best Threads in CCD Imaging & Processing", anyone with me ?
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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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I second that nomination!
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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: 142
Loc: Texas
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Aye. I believe the Bahtinov mask will raise the quality of all astro images and increase the joy we get from this obsession (I mean hobby).
And my wife says I can't focus, hah!
Ron
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-Ron
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Too much "stuff" and too little time to use it .....
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Joselo
sage
Reged: 02/26/08
Posts: 387
Loc: Texas
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I just hope whoever makes money out of this invention, will hold tribute/nomination to the true inventor. I believe strongly in fairness and equality, that is all I can say for now.
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APM 115 design by TMB
SV80S, and bunch of accessories
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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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Going square paid an unexpected dividend.
I wasn't really sure how I was going to seat this on the telescope. What I settled on was some thick pieces of foam tape intended for weatherstripping, that I just happened to have lying around. This stuff has adhesive on the back, and the triangular bits at the corners of the mask made ideal attachment points. I put a couple of layers on, and placed them inward from the ideal location so that there's a slight friction fit with outside of the telescope. Since they're soft foam and very elastic, it's easy to attach it to the scope with a firm grip.
- 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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Dubboy
Carpal Tunnel
Reged: 07/05/05
Posts: 2253
Loc: Northern Michigan
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Thank you, Dennis, for sharing this "revolutionary new way of focusing".
And thank you, Adam, for posting the work you have done in testing the method. I copy/pasted your refractor pattern to Photoshop and sized it to fit the cell that I made for a Hartmann mask.
Last night was clear with "not so nice" seeing and transparency. 
I used the Bahtinov mask on a Megrez 110 (focal length 655mm...f/5.95) in visual mode first and the results were great.
I then attached my Canon 350D with a 2.5x angle finder. If I remember correctly, the first,out-of-focus star is Vega and the fainter, closer-to-focus star is Alpha Ophiuchus (mag 2.09).
It was very hard to see the focusing pattern in the camera's finder so I adjusted focus until the faint "line" was sharp. My results are shown below. You can see that the first exposure is slightly off but the second is pretty close. The "test" images below that were taken at closer-to-focus. M13 at 30sec and M27 at 150sec. Both are unguided.
Because the camera viewfinder does not clearly show the focusing pattern, I'll still have to "shoot and check" but it will be a lot more accurate.
A big "HOORAY" to Pavel Bahtinov for sharing this with the astro community. 
"Jerry-rigged" test mask
Out of Focus
Closer-to-focus
M13...30 seconds
M27...150 seconds
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Don
"Don't worry about what telescope you own, or its quality. Just get out under the night sky and enjoy God's wondrous universe" Thomas Back.
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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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Hey Don, looks like your photos on PhotoBucket are password protected and cannot be accessed publicly.
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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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Dubboy
Carpal Tunnel
Reged: 07/05/05
Posts: 2253
Loc: Northern Michigan
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Quote:
Hey Don, looks like your photos on PhotoBucket are password protected and cannot be accessed publicly.
Hey Adam,
Thanks for the correction. My bad!!!
I went back and "cleaned up" my Photobucket album, deleting some pics...didn't know it would effect my post.
Can you see them now?
(
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Don
"Don't worry about what telescope you own, or its quality. Just get out under the night sky and enjoy God's wondrous universe" Thomas Back.
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jgraham
Postmaster
Reged: 12/02/04
Posts: 6694
Loc: Dayton, Ohio
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The image below shows my original modified Hartman mask on the right and my first draft of a Bahtinov mask on the left, both are from my SN6. The respective focusing pattern (an average of 0.1sec exposures of Altair using my DSI Pro) is shown below each mask. The pattern from the Bahtinov mask is much brighter and it is much easier to judge when the best focus is achieved.
This example Bahtinov mask was cut from black foam core art board using 5mm slots and slats. The angle of the reference slots are +/-20 degrees from the centerline (40 degree total internal angle).
My next task is to make a mask for all of my telescopes and see how well this works visually.
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-John
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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
Edited by jgraham (09/07/08 03:07 PM)
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snowdragonusa
Pooh-Bah
Reged: 09/04/07
Posts: 1125
Loc: Denver, CO
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Quote:
Hey Adam,
Thanks for the correction. My bad!!!
I went back and "cleaned up" my Photobucket album, deleting some pics...didn't know it would effect my post.
Can you see them now?
(
Looks great Don!
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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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Scott Mitchell
sage
Reged: 07/28/07
Posts: 259
Loc: Atlanta-ish, GA
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OK, I'll jump in too. I made my mask last night. I used a scaled version of Adam's graphic (thanks again Adam!). I scaled it up to a 9" diameter which resulted in 6mm openings. I went the for sale sign route since I happened to see them while I was at Home Depot getting something else ($1.40 for materials isn't bad). I actually like the material, although it does result in a funny looking mask on one side. The plastic is not too tough to cut and it has a decent amount of rigidity once mounted. I squared it off instead of cutting out the circle and super glued it to a cross stitch circle that I have previously used for my hartman mask.
And the results? It works pretty well! I could clearly see the middle diffraction spike moving to the center between the outer diffraction spikes. I was unable to resolve the 6 small circles when in focus like Dennis' original pictures. So a great improvement over my old hartman mask, but the focusing tool in the latest Meade Envisage seems to let me be a little more precise.
Here's my lovely work of art:
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blueman
Vendor Blue Sky Accessories
Reged: 07/20/07
Posts: 1391
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I read the thread and it seems a very interesting design
It seems to me that it works by a sort of interference pattern caused by the vertical line opposed by the 20° line to each side.
For masks I have been making and using string masks for a while. I wrote an article that was published about the various types of masks and included the cross hair string mask as my favorite.
So, I thought, why not try a string mask and see if the intersecting lines are the actual important thing.
This Bahtinov mask design though very nice and pretty too, is not an easy one to make. Thinking that there might be an easier solution I made this new string mask.
Hopefully I will be able to give it a try soon. A lot of Moon, but it may be worthwhile to just do something that would allow me to spot a bright star and look at it with the mask in place.
When I know something I will post again.
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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Luke S
member
Reged: 07/16/08
Posts: 65
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This method is fairly similar to something I have used for quite some time. If you have a newt or anything with a central mirror held with wires etc. you don't need to add anything, if you have a SC that doesn't have the support structure I have just put a piece of masking tape, running across the center of the aperture (not touching the correcting plate, just held up on each edge by the telescope tube). Then to focus, find a reasonably bright star and take a long enough exposure to get diffraction spikes, out of focus the diffraction spikes will be split, in focus they become one. Simple, effective and costs a roll of masking tape.
Edited by Luke S (09/08/08 02:20 AM)
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wr-astro
journeyman
Reged: 03/11/07
Posts: 6
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Quote:
... 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, ...
- Gus
Hi Gus
If the Hartman mask has round holes then there should be no real diffraction spikes (if nothing else like a spider vane causes them).
If the Hartman mask has triangular holes there should be just 2 (on both sides) * 3 (number of sides with differing orientation) * 3 (number of holes with differing orientation) = 18 diffraction spikes if the sides of the triangles point all in different directions. If you use equilateral triangles with sides that point in the same direction one will get just 2 * 3 * 1 = 6 diffraction spikes. Then it mainly matters just in regards of the brightness of the diffraction spikes if one uses just 2 or more of the equilateral triangles with aligned sides. I never understood why some guys recommended or used non-aligned triangle sides when they switched from round to triangular holes.
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Clear skies
Wolfgang
Edited by wr-astro (09/08/08 01:01 PM)
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isramirez
Pooh-Bah
Reged: 11/04/05
Posts: 1391
Loc: Mexico City
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A mate in Mexico, Pedro Gonzalez, created his Pavel mask for only $8USD, look
He is performing tests in his Maksutov as soon as weahter conditions improve here
Believe now is the proper time for chinese guys to contact Pavel Bahtinov and make the masks available at low costs for anyone around the world... $5USD maybe $6USD? or free if you gets a new scope? 
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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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Now that is one nice looking Bahtinov Mask!!! 
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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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Quote:
If the Hartman mask has round holes then there should be no real diffraction spikes
Of course not. Originally I was using circles, but after reading about the advantages of diffraction spikes for determining exact focus, I put a toothpick wrapped in electrical tape across each hole. This was a big improvement.
Quote:
If you use equilateral triangles with sides that point in the same direction one will get just 2 * 3 * 1 = 6 diffraction spikes.
The problem there is making sure the triangles are precisely aligned so the spikes overlap to give you just 6 instead of 18 spikes. The circle-and-toothpike solution was easier.
- 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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