ATM stopping down aperture

["J. v. Gastel" <m043653@home.vu.nl>]

I have often read that is good to stop down big aperture for looking at
planets or moon when seeing is not good. I have never tried, but I have
the following question about it. When stopping a 12 inch, with a 20%
central obstruction, down to 10 inch the central obstruction becomes 40
percent. So doing this gives less resolution because of less aperture
and less contrast because of very big obstruction. Maybe the image will
look more steady, but can one actually see more than with full aperture?

Jan.