Bahtinov Grabber - free focus aid software

[troypiggo]

Just came across this at Cloudy Nights (http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Board/Imaging/Number/2961332/page/0/view/collapsed/sb/5/o/o/fpart/all). Looks interesting and useful. Software that analyses a screen capture (updated 10x per second) and lets you know the accuracy of your focus. You need the mask, it just analyses the diffraction spikes by the looks.

Homepage of the software author with download link: http://www.njnoordhoek.com/?p=325

[Dennis]

Hi Troy

Thanks for that. FYI - this has already been covered in Msg#258 (http://www.iceinspace.com.au/forum/showthread.php?t=35676&highlight=Bahtinov&page=13)in this post (http://www.iceinspace.com.au/forum/showthread.php?t=35676).

Cheers

Dennis

[troypiggo]

Aah, hadn't seen that post Dennis. I did some searching for "Bahtinov" and "Grabber" in this section of the forum for previous mention of the software but got no hits. I was aware of your thread in the DIY section, but not the mention of the software - you can appreciate it's a massive thread with many pages of posts.

Regardless, I think it's a good idea to have this post here for someone who'll be searching the "computers/software" section for such software.

[Dennis]

Hi Troy

No worries – this is just a piece of “housekeeping” to keep the various posts connected. Updates and variations are always coming up on old themes – bless those creative minds, so there is certainly real value in bringing them up as fresh topics for a new audience.

Cheers

Dennis

[leon]

I think this is just going to far, focus is focus, and I can achieve this with ease without any use of any software or other device, and I'm nearly 60.

Just use your eyes. this image is achievable by sight alone

Leon

[dpastern]

Thanks Troy!

Love the title under your username btw!

Dave

[Dennis]

Hi Leon

Well, I just could not let this one go by!:lol:

I suspect that each person has their own story on the usefulness and benefits of Pavel Bahtinov’s focusing mask, or otherwise!:)

I have found the mask to be very useful in the following applications:

DSLR focusing via Live View with my Canon 40D.
Rapidly converging to the correct focus for CCD imaging with my SBIG ST7.
Obtaining accurate focus with my DMK/DBK CCD’s, particularly when using Powermates or Barlow’s from x2.5 to x4.

DSLR: Prior to the combination of Live View and the Bahtinov Mask, many of my images lacked critical focus and simply not knowing if I had the best focus before embarking on an imaging run was very unsatisfactory; often producing that nagging, unpleasant feeling of “I’m wasting my time”!

With my ST7, as I have to set up and tear down each time and use different optical tubes and Reducer/Flatteners, it was often frustrating establishing which side of focus I was at. Now, Pavel’s Mask has solved that problem and I can converge to the optimum focus rapidly and confidently and have this point confirmed by the software assisted focusing aids in the camera control software, CCDSoft.

When using my DMK/DBK webcams with PowerMates or Barlow’s I was often left wondering “was I at best focus?” because I could sit and twiddle with the motorized focuser for minutes at a time, trying to establish what I thought was the optimal focus. Now, using Pavel’s mask, I can zero in very rapidly and confidently, thus removing one of the more dreary elements of this type of astro photography.

So there you have it; Pavel is my hero and his mask is a constant companion on my outings! Now I’m not sure if makes me anal, or classifies me as a compulsive, obsessive type, but I certainly produce accurately focused images and enjoy that elusive peace of mind, once I have dialed in the focus using my Bahtinov Mask!:thumbsup:

Cheers

Dennis

PS – I commend you on your youthful, 60 year old eyes. What is your secret?;)

[h0ughy]

well there you go - something else to play with. BTW Dennis does it work from you post in the other thread? - Bugger you posted this while i was contemplating my navel and typing this out

[leon]

Dennis, OK, I have read your post, twice just in case I missed anything, and I read that you are happy and confident with the way you, and I expect others do their focusing stuff.

However Dennis, and others that may read this, I just don't use any aids in focusing at all, regardless of age.

I am not disputing that others may need some help in this area, but I just can't see the need for focus aids, sorry.

PS – I commend you on your youthful, 60 year old eyes. What is your secret?http://www.iceinspace.com.au/forum/../vbiis/images/smilies/winking70.gif

PS, no secret Dennis, I have just never gone there.

Leon :thumbsup: http://www.iceinspace.com.au/forum/../vbiis/images/buttons/quote.gif (http://www.iceinspace.com.au/forum/newreply.php?do=newreply&p=447806)

[Dennis]

Hi Dave

Yes, the links to “amateurs” CN posts still appear to work.

However, would it be possible for one of you most gracious Moderators, who hold the supreme power to modify all that is, to amend the Title of my original post (http://www.iceinspace.com.au/forum/showthread.php?t=35676)to include the reference “Bahtinov” as it is conspicuous by its absence!

Currently it reads, “Perfect focus each time – banish those focusing blues!” and maybe a more meaningful title could be:

“Perfect focus each time using a Bahtinov Mask”

Thanks!

Dennis

[leon]

Currently it reads, “Perfect focus each time – banish those focusing blues!” and maybe a more meaningful title could be:

“Perfect focus each time using a Bahtinov Mask”

But it can be done with out, the above. ;) :scared3:

Leon :thumbsup:

[iceman]

Done, Dennis.

Cheers

[troypiggo]

Leon, understand what you're saying. For the record, up to now I've been focusing my DSLR by eye. No live view. Just through the viewfinder. Last couple of times I've just used the Bahtinov mask to check. Surprisingly I was pretty spot on.

[leon]

Troy, I know what I'm saying, and the point remains that there is no need for these Masks, in a Fine Instrument of any make.

Surprisingly I was pretty spot on. I'm sure you were, mate, and that is my point :whistle: you don't need one......


Leon :thumbsup:

[jjjnettie]

I use 8 second shots taken at high iso to focus my camera. Zooming in after each shot to check. Then it's just a matter of "a little to the left, a little to the right" until you're there.
I've marked on the focuser where to achieve approx. focus for each of my cameras. This makes the process much quicker than you'd imagine.

[leon]

JJJ, thanks for your comments, and I appreciate your method of achieving the focus you need for that perticular imaging run,;) GOOD UPON YOU :thumbsup:

But the fact remains, the younger people of this forum rely on computer software to get them through.

It can be done, and is, many times over, just with the eye.

And I, will challenge any computer focusing software, to an eye focus in the same instrument, but, (I'm not talking a 60mm Tasco)

Leon :thumbsup:

[Alchemy]

you may have a good judgement of focus leon,

given i just bought one of these gadgets.... and which bloke doesnt like a few gadgets:D,
for me what i want is a simple confirmation its bang on rather than relying on my tiring old eyes. (note if i dont have my reading glasses on its hopeless), i used to use the diffraction spikes on the newt, having gone to a refractor the extra reassurance is nice.

will send you a link for my last image (not seen here), note i did this by eye and im not 100% sure i was bang on.

clive

[leon]

Clive, Clive my mate, I'm nearly 60, mate, it makes no difference if you have your specks on, or off, focus is still the same.

I too did think, because I was half blind and needed glasses to see, how would I go to focus a scope, mate just take Emmm Off, (your glasses that is) it works every time.

Trust me, ;)

Leon :thumbsup:

[Dennis]

This is proving to be quite an informative discussion. I found an interesting write up on “Focusing Methods for Astrophotography (http://www.astropix.com/HTML/I_ASTROP/FOCUS/METHODS.HTM)” on the website of Jerry Lodriguss. Out of the 17 methods of focusing that he discusses, he lists the eye as the least accurate method whilst the Bahtinov Mask only comes in at #6, with the Hartman Mask a lowly #4 on his list. The low ranking of these masks surprised me!:shrug:

Using Software Metrics was judged to be the most accurate, placed at the top of the list at #17.

I haven’t copied the ranked list, as Lodriguss’ website prevents this via his copyright statement, so here is the link (http://www.astropix.com/HTML/I_ASTROP/FOCUS/METHODS.HTM)to the write up. Well worth a read. I hadn’t realized that there were so many methods of focusing, although I guess we should now add the Bahtinov Grabber and the Carey Mask (http://www.iceinspace.com.au/forum/showthread.php?t=45396)derivative of the Bahtinov Mask, making the list 19 long!:lol:

Cheers

Dennis

[Alchemy]

ive already fessed up to having poor judgement of focus by eye. i spent 3.5 hrs shooting a subject just atiny smidge off perfect focus :scared2:

i have a program that comes with the camera (ccd)that gives a digital and graph representation, of FWHM ad brightness, BUT it dithers all over the place with the seeing. by eye looking at a screen that updates every 10 sec can i actually judge it perfectly ? using the mask - a line that bisects it and shows all the other bits, too easy :thumbsup:

given what ive used,eyes at the bottom, program (note its not automated that might be better), mask on top.

At the end of the day if it works thats all that matters.

[Dennis]

Yep – that about sums up my experience too Clive and I guess that’s the beauty of astronomy as a hobby – it’s a pleasant pastime that we can enjoy however we practice it; with different telescopes, focal lengths, cameras, accessories, preferences, skills and capabilities. Each person will adopt what works for them.

Cheers

Dennis

[leon]

I agree Dennis, ;) we all do it differently, which is good, so from this point on I will not mention another word :whistle:

Leon :thumbsup:

[Dennis]

Hey Leon

On no, please don’t do that….if you didn’t write another word, how would we all know that we are indeed different…and how would we continue to learn from each other about the assorted equipment and diverse techniques we use!:)

This whole discussion prompted me to go looking for some data on focusing and finding the Lodriguss website provided an interesting read.

My lack of patience and skills mean that I prefer focusing aids such as the Bahtinov Mask, but kudos to others who just eyeball it, or use other techniques; there is always something to be learned, and more often un-learned, through discussing these topics on Ice In Space.:thumbsup:

Cheers

Dennis

[Geoff45]

I had a quick read of this article. The trouble with his discussion of the Bahtinov and Hartmann masks is that he is talking about using them through the camera viewfinder, whereas most of us download the image and look at it on the computer screen.

[Dennis]

Hi Geoff

Good points. I do remember some while ago playing around during a couple of imaging sessions where I compared the focus accuracy of the Bahtinov mask by eye versus using CCDSoft Focus Tools. Unfortunately, the results were polluted by an ill-fitting mask and some (since) discovered slop in my focuser.

However, even with the above anomalies, I judged that to all intents and purposes, eyeballing focus via the Bahtinov Mask on my computer display was as accurate as using the Focus Tools panel in CCDSoft, where the software produces a graph indicating best focus. This was based on using a manually operated, motorized focuser, not a fully automated software controlled process.

Having now got a well made mask and having since solved the focuser slop, I haven’t yet re-run run the tests. Like you, my previous experience leads me to believe that the Bahtinov Mask would appear much higher up on my own list, when viewed on a computer display.

In other experiments, I found that even using the Canon 40D in-camera “Live View” at x10 zoom gives a superb focusing image using a bright star.

Cheers

Dennis

[leon]

Dennis mate, I didn't mean that I would never speak again, :lol: but just not on this subject.

To my needs and purposes the mask is of no value to me, considering my set up, the FSQ is so sharp, one can see it snap into focus. ;) and do It's diffraction thingy.

Leon :thumbsup:

Bugger, I just did, didn't I. :doh:

[Dennis]

Hi Leon

LOL! I knew that – you’re too much of an old hand at photography and astro photography and a strong character to boot!;)

When I find myself at variance with a particular view in a post, I am trying to leave a footprint that kind of says “that’s okay - what works for you doesn’t necessarily work for me” rather than “x is right and y is wrong” or “mine is the only way”.

Experience reminds me that several times, I’ve been out of order, plain wrong or just not understood the issues fully, (and not surprisingly this will continue), so my views are only what I understand right now, with the gear and techniques I have at my disposal.:)

Cheers

Dennis