Recent content by pegasusherd

Thank you both for these two great responses!

Hello, I am trying to understand the difference between Active IR and Passive Thermal Imaging. First, I'll start off with what I DO understand, and finish with what's confusing me: I understand that in Active IR, objects are illuminated with Near IR (NIR) light (695-1000 nm) and then...

Hello everyone -- thanks for your answers -- I think I now understand the issues. Primarily, I think that the part I was missing is that each point emits rays in all directions hitting every point of the mirror. Considering that one fact, it all makes sense. Thanks!

Two comments on the above: -You say no one ray represents a specific point on the object. I think this concept may be the one I'm having an issue with. So, why not? -Second, in addition to rays hitting the reflector coming in parallel, I'd imagine you'd also have some rays coming in at an...

Hello, I have a question regarding a Cassegrain style telescope (or any other "obscured" type telescope, for that matter). Can someone explain (in detail) why the small secondary mirror out in front of the large primary mirror does not cause some sort of a "blind spot" in the center if we...