Gary your a bloody legend! thats exactly what i wanted to hear. Everything i was reading was telling me that everything was good but i just needed that human repsonse that a book cant give! well... im getting the 10" SW where it needs to be for a imaging rig!
for the calculation of % illumination of a 40d Cmos sensor will be approximately 89% total coverage with a 27% central obs on a 254mm mirror. mmmm tasty!
thankyou once agian