a telescope with a diameter like mine with a CCD
camera attached has always been a challenge and
To improve this critical step I decided to build an
Internet enabled me to find a solution rapidly.
My Hartmann mask (also called a focusing mask)
is an essential mean to focus my LX200 GPS. It's made
of a disk of light wood with a diameter near the size
of the telescope.
There are four holes placed on opposite sides
with an angle of 90° each, to let the light go
through. The holes sizes do not matter at all.