Silly question

[Nath2099]

This is no doubt a silly questions, but can someone explain to me in layman's terms, if possible, why in reflector type telescopes the image doesn't end up with a black spot where the secondary mirror is blocking the light path.

Is it the same reason why you can't see blemishes on a camera lens unless you focus too it?

[bojan]

Exactly right.
However, you will see that black spot in the centres of star images when out of focus.

[Robh]

There is a focal point for the primary mirror. Every square cm of the primary mirror will focus the same image of the sky at this point. The additive effect of all these "little mirrors" will make a brighter image at the focal point. The larger the mirror the brighter the image.

Conversely, you can subtract lots of these little squares (e.g. where the secondary blocks the light) and it will just cut out a bit more light.
You could drill holes in your primary mirror and it would still work.

They can make really big telescopes using lots of smaller mirrors.
https://en.wikipedia.org/wiki/Segmented_mirror

Regards, Rob

[Nath2099]

Cool, thanks guys!