Bahtinov Mask

[MarkS]

I've just cut a Bahtinov Mask from cardboard and given it a test run on my Celestron C11.
This is the easiest way of focusing a DSLR I have yet come across (much much easier than the Hartmann Mask).

This thread on an astronomical website(and similar ones on the Cloudy Nights site) explains all:
http://www.iceinspace.com.au/forum/showthread.php?t=35676

Here is the one I made tonight:


And here's an animated GIF I created (using the DSLR on the C11) that shows it in action - it is the image of a single star with the Mask placed in the front of the scope:


When the vertical bar is central between the slanted ones then you have perfect focus.  The other great thing is that it even "tells" you which way to turn the focus knob - turn it one way to move the vertical line to the left, the other to move it to the right.   It couldn't be easier!

[Ian]

now that looks scarily useful...

[RobertM]

It's brilliant, I've been trying it out the last couple of sessions and it certainly works much better than the mask I've been using till now.  Mine's rather crudely made out of part of a cardboard box but still works a treat.

[Tony G]

I can feel a Blue Peter moment coming.
Might try this the weekend.

Thanks Mark.

Tony G

[Mike]

Looks interesting. I will give that a go myself.

[Mac]

Found this whilst searching for things astronomical.

http://astrojargon.net/MaskGenerator.aspx

it will generate your masks for you.

[Carole]

I've made the 3 hole version focus mask.  Would any-one say that this mask is even better.  I found the 3 hole version worked perfectly for me when I used it. 
Just wondering whether I should make this one as well?

Carole

[RobertM]

For the extra accuracy it's definitely worth the effort.

[mickw]

How precise does the cutting have to be, or is it the pattern that does the trick ?

Cutting one for a 91 is doing my eyes in

[Mac]

or is it the pattern that does the trick

Its the pattern that works, by using diffraction.
similar to the once you see round stars

cutting dosent have to be that accurate, resonable should do.
all you will get is a slightly different difraction pattern.

[mickw]

Thanks Mac

That's a relief 

[Mike]

Just realised I can get these laser cut at the London Hackspace in perspex or MDF. Will have to make one for my ED80.

[RobertM]

I have a couple that need doing, any chance of getting those done while you're at it ?

[Mike]

Sure. Give me the details.

[RobertM]

Thanks, I'll need to get some perspex and mask layout to you.

When are you getting them done?