Having just got my evostar ed80 and not having a suitable Bahtinov mask for it I was going to make a smaller version but then I found this great article on the forums about making a much easier and better mask The Lord Mask
First read this article by the chap who says this..
I trust this primer in Fraunhofer diffraction demonstrates how the Bahtinov mask
functions, and how a superior mask consisting of a 'Y' shaped bar serves exactly
the same purpose, but to better effect.
So save yourself the time and effort in making a Bahtinov mask, or save your
money. Instead make a 'Y' shaped mask. Perhaps you could recognize the man
who pointed out this economical alternative and christen it the "Lord" mask
So armed with this info I then set about making my own.
You will need an old DVD case a craft knife and pencil.
First mark out on the dvd case your circle using the dew shield from you ed80
Next mark out a cross in the centre in pencil
Next mark out the Y shape using a 20% angle for the top bars
When that is cut out you can also cut out the middle section of the DVD case the bit that holds the DVD that just happens to fit nice and snug around the outside of the Dew mask if you cut it carefully with a craft knife then stick your Y shape on it with some black tape and you have neat little Y shape Lord Mask that clips on an off the dew mask with ease.
Job done and cost nothing to have a focusing mask for your ed80.