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?
Chris, nah the secondary mirror is relative small, in area, compared to a 250mm diameter mirror.
While there are some contrast effects which can come in to play with large obstructions, visually-intended newts don’t tend to have particularly large secondary mirrors.
You lose aperture and as you get faster newts the secondary gets larger and you can lose resolution as well. A planet newt can have a 15% or smaller secondary, a very fast AP newt 25%.
But what you lose by the secondary in a newt you gain in the aperture many times over in regards to aperture per dollar.
Ps. A 10" has four times the light gathering capability of a 5".
