Hi all,

Some of you will have already seen the below images in one of my other threads but as I am so impressed with the performance of the focus mask, I thought I would re-post them as a seperate thread in the hope that it will be seen by more people who might in turn benefit from the knowledge as I have.

As many will know, I was really struggling to focus my C8 SCT but as a result of some advice from fellow forum memebers I dowloaded a free focus mask template from Bahtinov Mask by Focus-Mask and cut a crude mask out of cardboard to see if it worked and it really does ! Now that it has proved itself, I will eventually take greater care in making a further mask out of a slightly more durable material.

The idea for those who don't already know is that as you alter the focus of the scope, the horizontal light rays move up or down depending on the direction of focus. Perfect, (or very near perfect), focus is achieved when all of the light rays converge in exactly the same place.

To illustrate this I have attached:
(1) An image of the bright star I used to focus
(2) An image of the star viewed through the mask with the scope out of focus.
(3) An image of the star viewed through the mask with the scope in focus.
(4) An image of my crudely produced cardboard mask.

Before this mask, DSS would not properly stack any of the subs produced from my C8. However with the mask, not only do the subs stack in DSS, but the resulting image is the sharpest I have taken of M3 with any scope so far, (see this in the Deep Space imaging section)

Assuming that there is a suitable mask template for your scope, why not give it a go ? especially as it costs nothing but time to make

Ian

I agree Ian - the masks are great! I'm going to do one now for the C8 in Fastar mode as focus is critical at f2!! Wish me luck with my cutting - I'm sure it'll be well worth the effort though!

Helen

I'm already converted, twice in fact

Dave

I've made one for each scope from laser-cut acrylic..
Works equally well on refractor and SCT.

They are "nice" aren't they...

BILLY....

Ian
Thanks for the info, I have printed off the template for my ED80, so will give it go.
Just started imaging with my DSLR and must admit that getting the focus right is certainly frustrating.

Cheers
Ron

Another thumbs up here! It has transformed my imaging.
One of my most important bits of kit, which is saying something for a flimsy bit of card I cut out

Without doubt the Bahtinov mask works extremely well and focus is just such an important attribute to get right - well worth the time with an 'x-acto' and a cutting board.

Thanks for the heads up on this, i find focussing my DSLR very difficult. Will give this a go.