[SB (Chris)]

Hi All,
I have a question about Newtonian Reflector aperture specs.

Is the stated aperture (say 250mm) reduced by the secondary mirror? I was pondering this when reading the comparison of light collecting ability between a 100mm refractor and a 250mm Newtonian. Given the secondary mirror can be quite large blocking incoming light, wouldn’t this reduce the effective aperture resulting in an aperture less than that in the stated specifications?

Thanks

SB