Bahtinov Focus Masks

[h0ughy]

I have been involved with a friend from QLd in developing a design from the original idea and design of a revolutionary focusing mask by a Russian amateur astronomer, Pavel Bahtinov.:bow: The mask consists of a pattern of solid bars with equal width spaces between the bars. One side of the mask has horizontal bars, the other side has bars tilted at angles of ±20°. discussion of this has been going around the traps, like on cloudy nights (http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/2544487/page/0/view/collapsed/sb/5/o/all/fpart/all/vc/1) and a few russian (http://astrophoto.chat.ru/) sites (http://www.astronomy.ru/forum/index.php/topic,10421.280.html).
Tthe quote to have 8 variable sized masks cut out of 304 grade Stainless steel will cost $192.50 making them on average $24.06 each for this batch. Obviously the larger ones would be dearer normally. I think this is excellent value for money - and an economical way of getting a decent focus mask. Just letting you guys know or become aware:wink::tongue:. I have ordered a mask for each of my imaging scopes (10" LX200R, C8, Vixen R200SS, ed80 and the 127ED) the others are dennis's (mewlon 180, c9.25 and the vixen 102). have to paint them flat black when i get them, add some felt patches on the side to go near the objectives and add a little pin to hold the mask with. but essentially the hard work will be done wit hthe laser cutters and nice straight edges!! not handcut by Mr all thimbs!!!

[Radar]

I imagine you'd be better off with a ronchi screen Dave. Easier to move around, more compact to use.

Ray

[h0ughy]

I imagine you'd be better off with a ronchi screen Dave. Easier to move around, more compact to use.

Ray
Ray, I realise that this is a IIS link but please have a look at how this "gadget" performs http://www.iceinspace.com.au/forum/attachment_browse.php?a=47446

it is an annimated GIF made by Dennis Simmons, showing how quickly focus can be achieved with the mask. It sold me real quick!! I drew up the design for anyone that wants it, the CAD DXf file is there so that anyone who wants one can go to their local laser cutting manufacturer and get a mask done.

[seeker372011]

Ray

this is the greatest thing since sliced bread

Ted from my astroclub had one last weekend and showed me how good it is on his C11

I leaves all his fancy 3D Maxim focusing software for dead-and is not dependent on seeing too.

It is far superior to an ordinary Hartmann mask

I have made myself one out of foam board but its very rough and ready as you cant cut this material very neatly

I make try again using the material that real estate signs are made off..but really for the hours its likely to save in the field it is a very handy accessory

[seeker372011]

so could I get one or two, Houghy at that price of $25 each?one for my ED80 and one for the ED 127- i dont even have to measure them you ahve the same scopes ;)
Narayan

[Radar]

Okay so this is the same principal as using a hartmann mask, but with all the gaps and cutouts, it makes focus easier or more accurate or both?

Also what is the weight of this? How bright does a star need to be for focus?

Could probably be used for collimation to.

Ray

[h0ughy]

so could I get one or two, Houghy at that price of $25 each?one for my ED80 and one for the ED 127- i dont even have to measure them you ahve the same scopes ;)
Narayan I have posted the DXF file if there is a local laser cutter you could get it done Narayan, else PM me some details and I will see what i can get done.

[h0ughy]

Okay so this is the same principal as using a hartmann mask, but with all the gaps and cutouts, it makes focus easier or more accurate or both?

Also what is the weight of this? How bright does a star need to be for focus?

Could probably be used for collimation to.

Ray
its only 1.2mm stainless steel so wont be that heavy. i will weigh mine when I get them. not too sure on how bright the star should be

[DarkSkyMan]

Be good to see one of these in practise. Sounds very promising, I'll say that.

[seeker372011]

Ray

the beauty of it is that if your test star is not too bright you can increase exposure duration

this is one of the things that normally drive me nuts--obviously FWHM is dependent on the exposure duration and seeing so just looking at that stat alone makes it hard to know when you are in focus

with this you can focus just as easily with a H alpha filter in place as without

[DarkSkyMan]

Been doing some research on this unit, very interesting. I think I'm going to make one.

Brett

[h0ughy]

Been doing some research on this unit, very interesting. I think I'm going to make one.

Brett
good for you - you wont regret it

[h0ughy]

here is the finished product. might look rough but they are diamonds:wink:

[trevorw]

I've tried these frames and they appear to work quite well although with smaller scopes it is still difficult to ascertain when a perfect focus is acheived.

However I've also tried varying adaptions of the Hartmann mask and they seem to work just as well especially for my smaller objective and short FL scopes.

In my opinion Bahtinov has only improved upon the Hartmann mask but knife edge and ronchi screens are still more affective in obtaining perfect focus particularly for those with less than perefect eyesight.

:woot:

[derrybawn]

When I open the dxf file in Autocad, I only see masks for the 10"Lx200 to the mask for the ED80. This is the top row of masks from the pdf file. I need the bottom row, specifically for the c9.25 & the Vixen 105. Can anyone help?