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This is one of the misunderstandings that is common when starting out with an obstructed scope like a newt... everyone looks at the central obstruction and wonders why they can't "see" it when looking through the eyepiece at a focussed image...
It takes a bit of a thought experiment to sort this out, let's assume that you've got the scope pointed at a point source a long long way away, eg a star. Light from that star comes into the end of the scope, hits all the exposed parts of the primary (ie all except the central bit that's in shadow) and then bounces up to the secondary, is reflected into the focusser and comes to focus as a single point of light at the focal plane.
The first thing to realise is that all the rays of light that make up this point have come from all over your primary mirror. ie *all* of the unobstructed part of the primary contributes light into this single point that you look at through the eyepiece. It's not just coming from one part of the mirror.
Now imagine a second star, close to the first so that it's also visible in the same eyepiece. The rays of light from that star have also come into the scope and hit all of the unobstructed portion of the primary, but from a slightly different angle. As a result they bounce back up the tube and come to focus at a slightly different location to the first, but just like the first star *all* of the available mirror surface was used to form the final image.
Think about this for a while and it should become clear why you never "see" a black hole in the middle of any in-focus image, since every point in your field of view was formed the same way - ie by using all of the available mirror area, it's not possible for some parts of the image to have used a different bit of your mirror compared to any other part.
cheers, Bird
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