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Post by davy on Aug 8, 2019 21:02:04 GMT
Finished the bahtinov mask design for the ed80 tonight,, posted design in astronomy Scotland Facebook group and they likely, been asked if I could do it clear,, thought the chap was taking the proverbial -iss ,, you actually can get them,, nearly £50 + delivery,, straight on to eBay,, roll if clear stuff in its way lol
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Post by davy on Aug 8, 2019 21:08:52 GMT
Got chap wanting one made for the sw72,, now that's no hanging around lol
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Post by Dragon Man on Aug 9, 2019 12:55:26 GMT
Yeah davy, the colour doesn't matter. Even clear, because it uses the knife-edge cuts to show diffraction spikes. Same as using fishing line to make diffraction spikes on stars with a refractor.
Actually, a clear one would work better because it would allow more light through. The opaque ones cut light a lot in the process of making the diffraction lines.
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Post by davy on Aug 9, 2019 13:49:40 GMT
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Post by Dragon Man on Aug 10, 2019 14:40:31 GMT
That's a perfect example
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Post by davy on Aug 11, 2019 14:30:04 GMT
Made a start,, printing prototype in white to see how it looks
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Post by davy on Aug 11, 2019 17:06:19 GMT
Few bits to modify, skirt detaching from front, think it's a software issue and need more of a lip to hold on scope,, Worked out well for a prototype
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Post by davy on Aug 11, 2019 17:07:12 GMT
Redesign then design one for canon lenses I use
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Post by howie1 on Aug 12, 2019 12:30:40 GMT
Redesign then design one for canon lenses I use Give it a go davy, but I think you will find the normal bahtinov design does not throw a good spike when down at the scale of fitting a canon lens. My flyscreen masks, however, do throw a great spike when made for the size / aperture of the canon lens! That's what I found when trying both. The flyscreen mask lets heaps more light through than the bahtinov commercial/online designs. Flyscreen throws a much better spike in order to focus with. But, I've achieved great focus without using a mask at all and instead using the following method. Set auto focus button on the lens. When you set it the lens does NOT not try to focus automatically ... BUT it is now under control of EOS Utilities! And thats the beauty ... as in EOS Utilities it allows you to click a < "button" and a > "button" on the EOS Utilities focus window. Each "button" press "steps" one small focus movement in the lens using its motors. IE you get a remote focus device. In Liveview, you click the EOS Utils 5X zoom button and then the 200% button so you can see the star at 10x mag. Then without going to the lens at all, you sit at your PC and just press the < or > in EOS Utils until you get the smallest star (or centre that diff spike if you really are keen on using a mask). I've found better results just minimising the diameter of the zoomed star. Less stuff to carry around and make too as you do not need a baht mask at all. CAUTION: once focused you must go to the lens and turn OFF the auto focus button on the lens. Otherwise when you slew to your target the lens will try to autofocus and you'll loose the focus point you just setup! I've achieved the best focus with the canon DSLR using this method of liveview, 10x zoom, setting auto focus button on the lens, then using the EOS Utilities <> focus buttons to get the smallest star on screen, then turning off the autofocus botton on the lens. cheers
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Post by Dragon Man on Aug 12, 2019 12:49:43 GMT
If a Canon lens is out of focus, the BEST way to get it to perfect focus is to package it safely in a padded box and send it back to Canon with an accompanying letter informing Canon that their lens is out of focus. Ask if they could please Focus it and send it back to you 'in focus'. Sheeesh! You pay a lot of money for good lenses, you'd think they would get the focus right For anyone not getting the point, this is a joke! Like if a piece of string is too short on one end, cut some off the other end and tie it onto the end that is short. Fixed!
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Bahtinov
Aug 12, 2019 19:18:03 GMT
via mobile
Post by davy on Aug 12, 2019 19:18:03 GMT
Hi Howie,, was printing original bahtinov mask to take to Galloway forest,, if it got lost or broken,, no big deal,,I would have my hang in one I bought. Can remember your fly screen post..
You know me,, get bored easily 😁 So got to thinking on what you said,,,fly screen let's in more light,, and I thought,, would letting more light in on original bahtinov be the answer.. Who knows,, 😂 certainly not me but,, being the inquisitive type ,, I removed a few bits on original design and wondered if it would work,, I know that it's easier to look through small thin mesh than thick and it also let's in more light,,but would this work.
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Post by davy on Aug 12, 2019 19:18:48 GMT
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Deleted
Deleted Member
Posts: 0
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Post by Deleted on Aug 13, 2019 4:40:18 GMT
Just guessing Davy as I have no idea.I reckon the diffraction spikes will be extremely narrow and could barely be seen.As the gaps get narrower,the diffraction increases until full diffraction when the gap is about the same size as the wavelength of light. cheers Paul
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Post by davy on Aug 13, 2019 5:21:13 GMT
Thought more on it and came to same conclusion,, may not be enough defined spikes to work,,saw somebody has done a fly screen one on 3d printer on sgl,, too much hassle just now but,, will follow up Howie's suggestion,, but will print out a frame in clear pla and use the mesh, In the meantime, I tweaked original design and will print in clear pla on Thursday
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Post by davy on Aug 13, 2019 5:23:24 GMT
Changed print settings to see how it prints and have design printing in just over an hour instead of nearly three
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Post by davy on Aug 16, 2019 6:57:21 GMT
Update on the clear pla mask... It's not a success,, it got printed out and it's not far off white looking to be honest, certainly isn't transparent,,but it answers the question lol, would it be better and answer is no,, the mask design is fine and good to have that if needed can print one off in various sizes.
Is this the end,, of course not Had my suspicion from the start it would not be see through and have a alternative to try,, I bought in laser cut acrylic circles, in various sizes and have two the exact size of the dew Sheila if the ed80 and will try and laser cut the bahtinov design on it.. What I think may happen is the acrylic may warp due to the heat.
And if that happens,, lol I bought fly screen to try Howie's fly screen design,, I would 3d print a body to fit the fly screen on,, and it's scalable so,, this will definitely work ,, Howie said so 😁
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Post by howie1 on Aug 16, 2019 11:15:45 GMT
LOL! davy ... with the smaller lens size flyscreen masks do NOT have the central divide at all. Just overlap the two halves of mesh by just one or two small square and then ... get a needle and fine cotton thread. Run the thread through epoxy, and then "sew" it up through the single small quare overlap area and leave to dry. It ends up looking like the one in the photo.
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Bahtinov
Aug 16, 2019 15:58:01 GMT
via mobile
Post by davy on Aug 16, 2019 15:58:01 GMT
Excellent advice as always mate,. Your video is getting a few bits from folk on the scottish astronomy Facebook group, drop in and say hi,, nice bunch of folk
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Post by howie1 on Aug 16, 2019 23:02:58 GMT
Which one on FB davy? Highland Astronomy? Amateur Astronomy Scottish Borders? Astronomy Scotland? I started reading through posts but thought i'd save time and just ask you which group! LOL
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Post by davy on Aug 16, 2019 23:24:10 GMT
Astronomy Scotland
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