I have seen some sifus using a focus mask for AP focussing. I decided to make one myself using the mask generator at:
http://astrojargon.net/MaskGenerator.aspx
This is the mask for a 127mm ED refractor
A out-of-focus Sirius
A focus Sirius
Build Your Own Bahtinov Focus Mask
Re: Build Your Own Bahtinov Focus Mask
Congrats and thanks for sharing the link!
http://www.astro.sg
email: gary[at]astro.sg
twitter: @astrosg
"The importance of a telescope is not how big it is, how well made it is.
It is how many people, less fortunate than you, got to look through it."
-- John Dobson.
email: gary[at]astro.sg
twitter: @astrosg
"The importance of a telescope is not how big it is, how well made it is.
It is how many people, less fortunate than you, got to look through it."
-- John Dobson.