Black Light from Shadow?

Is there such thing as black light?

Well. When you look at the eyepice of an SCT. You can notice
the central obstruction at the center field reducing the
contrast in the image. I'm not talking about the exit
pupil with black hole at the center but the central
obstruction directly affecting the eyepiece just like
flares from baffleless tube. These are called off-axis
light. The flares from the tubes are off axis-light. Now
the central obstruction produces also an off-axis effect
directly inpinging on the eyepice. Now. What kind of rays
from the central obstruction hits your eyepiece? It's colored
black, how can it affect your view? Are their black lights?
I know about image formation so you don't have to repeat it.
I know the image you are getting from the eyepiece comes
from on-axis parallel lights from the objective lens and
exiting in the eyepiece as parallel rays which upon touching
your cornea converges into a point in your retina. Hence.
The central obstruction is not supposed to cast a
shadow at the center field of the eyepiece. I'm talking
of any focal length eyepiece and any magnification. Can
anyone explain this? I mean when you look at the image,
does the image depend on having a clear aperture at the
front. What I mean to say is, why does the central
obstruction degrade the view from the on-axis parallel
rays when the output from the eyepiece is just a result
of what comes before the objective lens and not the
central obstruction. Again don't mention about exit
pupil with the hole in center because this is not what i
mean. I'm talking about the off-axis intrusion of the central
obstruction. It's black and doesn't produce lights versus
the flares. But it can still affect your view. Why?

Does anyone understand what I'm describing?? If not. Let
me know and I'll explain further.

Wat