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Revolutionary new way of focusing! No less!

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#201 isramirez

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Posted 08 September 2008 - 08:00 PM

Now that is one nice looking Bahtinov Mask!!! :jump:


Bet that Adam :) it is 100% inspired on the first file you sent me :waytogo:

#202 snowdragonusa

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Posted 08 September 2008 - 08:08 PM

Now that is one nice looking Bahtinov Mask!!! :jump:


Bet that Adam :) it is 100% inspired on the first file you sent me :waytogo:


Cheers mate!

#203 jgraham

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Posted 08 September 2008 - 09:41 PM

Wow, that's a nice looking mask. Much better than my hack.

#204 cvedeler

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Posted 08 September 2008 - 10:29 PM

A mate in Mexico, Pedro Gonzalez, created his Pavel mask for only $8USD, look
Posted Image


Is that made out of black foam board? If not, what is it made of? It looks really nice. Much nicer than my attempt. Perhaps you and your mate could open an export business. I know I would be interested.

#205 John Wunderlin

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Posted 09 September 2008 - 09:37 AM

I used the mask to image the beginning DSO contest this month- best focus I've ever had in a Deep sky object, and it took me under a minute to get it!

Here's a link to the full resolution version. You have to click on the magnifying icon to zoom in.

#206 mikefulb

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Posted 09 September 2008 - 02:30 PM

I did some more tests with my mask last night operating at 500mm (f/2.8) on my Epsilon.

I discovered that best overall focus (reported by ccdinspector) occurred when the lines did not quite intersect. This struck me as odd.

My only idea is that the camera is tilted very slightly and so to reach best overall focus over the chip I have to slightly defsous the center.

So I moved the star into all corners of the CCD but the diffraction pattern did not change enough for me to detect by eye.

I'm wondering if at f/2.8 the critical focus region is so small its going to be difficult to visually detect differences.

Has anyone focused a telescope faster than f/4 with this mask?

#207 Mert

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Posted 09 September 2008 - 03:26 PM

Hi all,

Just finished a little drawing to make a mask for my
Mak 6"/F12 so the spacing calculated would need to be
6mm ( 6mm gap and 6mm spacing ).
Would this work ok?

Attached Thumbnails

  • 2633120-Bahtinov.jpg


#208 snowdragonusa

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Posted 09 September 2008 - 03:33 PM

I did some more tests with my mask last night operating at 500mm (f/2.8) on my Epsilon.

I discovered that best overall focus (reported by ccdinspector) occurred when the lines did not quite intersect. This struck me as odd.

My only idea is that the camera is tilted very slightly and so to reach best overall focus over the chip I have to slightly defsous the center.

So I moved the star into all corners of the CCD but the diffraction pattern did not change enough for me to detect by eye.

I'm wondering if at f/2.8 the critical focus region is so small its going to be difficult to visually detect differences.

Has anyone focused a telescope faster than f/4 with this mask?


Curious...

What was the gap you used between each cut out? If you do a 3*500/150=10mm then you should have 5mm between each cut out slit. Was the mask bent or warped at all?

Cheers,
Adam

#209 isramirez

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Posted 09 September 2008 - 04:08 PM

Is that made out of black foam board? If not, what is it made of?

As i know it was made of 3mm wooden MDF and then black painted

Perhaps you and your mate could open an export business. I know I would be interested.

We understand the business side is reserved only for Pavel Bahtinov... i'm sure the chinese companies as Synta, GSO, etc. can easly provide masks for every single scope available worlwide at a very affordable cost :) think they just need to contact Pavel Bahtinov in order to ensure expert advice from him :grin:

#210 cvedeler

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Posted 09 September 2008 - 04:21 PM

I just found this site:
http://www.stencilso....com/index.html

Looks promising. I'm waiting for a quote.

#211 Jerry3672

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Posted 09 September 2008 - 05:50 PM

Dr Mike-It is very important that the cut outs are a mirror of each other and centered to the optical axis. Check and see if your lines are straight. Trace out your mask on paper and then flip it face down and see if the axis is centered and the lines are a mirror.


Mert- Your horizontal cuts should start in the center axis and mirror out. I think the odd spacing of the cutouts will make the diffraction spikes wide. they still will be in the center if the axis is centered, but may be too wide to see a clear difference between the angled and straight spikes.

isramirez- Contacting Pavel is more difficult that I thought. I've made an attempt, but without speaking Russian it is very difficult. Maybe someone will invite him to join cloudy nights. :jump:

#212 mikefulb

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Posted 09 September 2008 - 06:44 PM

I did use the 10 mm spacing as you suggest. I don't believe there was significant warpage but it is something I will investigate next time out.

How sensitive do you think the mask is to warpage?

#213 jimguy08

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Posted 09 September 2008 - 09:02 PM

Here's one of many online custom laser cutting businesses:
http://www.customlasercutting.com/

#214 blueman

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Posted 09 September 2008 - 09:06 PM

Let us know what happens with the stencil cutting, that would be a great way to get them made cheaply.
Blueman

#215 snowdragonusa

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Posted 09 September 2008 - 09:25 PM

I did use the 10 mm spacing as you suggest. I don't believe there was significant warpage but it is something I will investigate next time out.

How sensitive do you think the mask is to warpage?


Actually Mike, I think your issue is the placement of your 90 degree center line. If you look at its placement you will see it is just slightly off center to where the V of the 20 degree lines meet. I think this is the fundimental reason behind your 'just off center' defraction pattern. Try another go (or just rescale the one I had posted earlier) and see if that helps with the fast f/2.8 of your scope.

Cheers!

#216 DugDog

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Posted 09 September 2008 - 11:23 PM

With Adam's file, I create my version of the "Amazing Bahtinov Mask".


First I taped the pattern on a 2MM Thick black Foam Sheet, cost 0.42 cents per 9 X 12 Sheet. This project required two sheets 0.84 cents.
Posted Image


Took an exacto knife, and cut out the pattern on the foam sheet.
Posted Image


I made a sleeve out of the foam sheet too, and then mounted the mask on the foam sleeve...packing tape to seal the sleeve to the mask.
Posted Image



Here it is mounted on the scope...had to buy some "Glow in the Dark Stars" to put some bling bling on the sleeve. Cost $1.96 for the bling...ouch, had to pay big bucks for the bling, but it looks kewl :grin:
Posted Image

Total cost = $2.80 (with the Glow in The Dark Stars).

Next I will have to do a first light test.

I must thank Adam :bow: for making a cool file, and I must thank Dennis :bow: for always coming to these forums with great topics!

DD

#217 snowdragonusa

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Posted 09 September 2008 - 11:29 PM

Awesome bling Doug! Nice job! :jump:

#218 akira

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Posted 10 September 2008 - 12:36 PM

hi i'm new to this forum and i followed this link from another forum. my questions for this mask are two

1. since i am the owner of an 8'' dob and i am starting astrophotography with an heq5 pro mount do i need this mask for focusing or is it only for SCTs, MACs etc?

2. the angled bars are at 40 degrees from the center of the of the mask or 20 degrees (i saw this value at another forum)

#219 mikefulb

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Posted 10 September 2008 - 12:46 PM

Thank you for this information. I had made the mask in Photoshop and I didn't realize there was an offset. Is there a mathematical expression to determine the offset of the central line from the tip of the triangle?

I'll try scaling one of your bitmaps and using it as a comparison with my current mask.

#220 John Wunderlin

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Posted 10 September 2008 - 01:03 PM

Woohoo!!! Jerry was able to make contact with Pavel and we've received permission to include his name on our site. I've added text describing the history of the mask. Again, I apologize to Pavel and everyone else here for not having this ready on day 1.

#221 John Wunderlin

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Posted 10 September 2008 - 03:36 PM

1. since i am the owner of an 8'' dob and i am starting astrophotography with an heq5 pro mount do i need this mask for focusing or is it only for SCTs, MACs etc?


I can field the 1st part. The mask will work well with any type of scope. If you have spider vanes, their diffraction spikes will also appear, but are much, much dimmer than the triple diffraction spike pattern and do not interfere.

#222 jgraham

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Posted 10 September 2008 - 04:02 PM

The angled bars are at +/-20 degrees from the centerline.

#223 snowdragonusa

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Posted 10 September 2008 - 06:09 PM

hi i'm new to this forum and i followed this link from another forum. my questions for this mask are two


2. the angled bars are at 40 degrees from the center of the of the mask or 20 degrees (i saw this value at another forum)


The original design Dennis presented (and I believe might be directly from Pavel's) the diagonals are at a + or - 40 degree angle. The mask I made is using a + or - 20 degree angle. The big difference will be the resulting total area between the diffraction spikes.

Cheers!

#224 snowdragonusa

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Posted 10 September 2008 - 06:20 PM

So, I have received many requests for the scalable vector graphic drawing I did for the Bahtinov Mask. So I figured I would post the 'email' I was sending everyone and include the actual files here so anyone can download and use them. Please do not use my drawings to produce masks to sell. These drawings are provided to the community as open source and should always be treated as such. :grin:



Hello!

Thank you all for waiting. I must apologize in advance. I had made a mistake in the asking the size of aperture on each of your scopes. I actually needed the full front diameter of your scopes so the mask can sit in front without leaking light in through the sides. I suppose it isn’t that big of a deal but I also didn’t want to send you a useless size.

So I have included the scalable vector drawing that I made. This way you can simply scale it to the exact size you need with out waiting. You will need to download and install Inkscape if you haven’t already. Alternatively you can import the file in to any other editing software that supports svg files (scalable vector graphics) such as Corel Draw.

In addition I have included a new drawing I did that is more designed for refractors. The central obstruction is greatly reduced to allow more light through. Please let me know how it works out if you try it.

Once you have Inkscape installed simply open the svg file. Select the arrow tool in the upper left side and click on the mask. On the far right side of the measurement boxes near the top middle of the screen, change the ‘px’ selection to ‘mm’ – this is your measurement unit. Next, in the right two measurement boxes, enter in the diameter of your scope opening. Enter the same number for both boxes so your mask is a perfect circle.

Click on “File” and export your resized mask as a bitmap. This will allow you to more easily print out your new pattern from your preferred printing program. Here is a screen shot with the items I just mentioned circled.

That should get you a nice new mask to try out. Whether you print it out on paper and cut it out or you have one cut for you, please let me know how it works out for you! Please let me know if you have any questions!

Cheers!


This is the scalable vector graphic for the SCT Bahtinov Mask.

SCT Bahtinov Mask Vector File

This is the scalable vector graphic for the Refractor Bahtinov Mask.

Refractor Bahtinov Mask Vector File

Here is the screen shot mentioned above to show where the InkScape commands/buttons/options are.

Cheers!

Attached Thumbnails

  • 2635604-screenshot.jpg


#225 blueman

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Posted 10 September 2008 - 06:37 PM

I decided to make of of these masks today. So I printed the one posted for refrators and scaled it to 4.75" which is the inner diameter of a 5" plastic pot for planting. Then I cut a piece of .032" ABS and pasted the printed drawing on to its surface. Then I cut the channels from there edge to the inside with a pair of tin snips, small ones like scissors. Then used a exacto knife to cut the small ends left of the channel cuts. Once I removed the channel cuts, I had a mask and removed the pasted on paper printout. Next, I used a hair drier to heat the ABS which makes it go back to its original shape, eliminating any slight bending resulting from the cutting.
Next I cut off the bottom of the planting pot, so that it would just slip into the dew shield of the 80mm APO. Then I used hot glue to glue the cut out mask onto the step lip on the top of the pot. Then painted it flat black inside and out.
Looks pretty good, cost was about $.25 for the pot and I had the ABS laying around as a scrap from items that I make for people.
The next time I go out I will give it a try along with the other mask I just made to see which works the best. I will post what I find.
Blueman.


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