I think I have fundamental confusions with how VLBI works. I don't know why:
Resolution increases when incident rays meeting to a focal point from a farther separation along an axis perpendicular to their travel account for greater resolution of an image
How interferometric fringe patterns matter to us. Yes, if you vary phase difference between two telescopes a fringe pattern can be ascertained, but I don't see how this is important. To my eyes, apparently with the image below from Bob Campbell's So you want to do VLBI:
I'm assuming that the reason why the
dotted rays are lost
is because there actually is no "lens" anywhere except where the the two darkened portions are. Otherwise, that is how I would expect rays going that way would travel with a lens, which was confusing. I will assume it's because we are isolating just the darkened portions of the lens and disregarding everything else. Now, I understood this as, as the darkened portions are separated, the resolution improves (where again, I don't know why). Is this where separating telescopes far away comes in to improve resolution? If so, why can we consider antennae as the darkened portions of that figure? They're parts of a lens. Perhaps I've got it all wrong, and those two darkened portions correpond to darkened portions in one satellite/telescope. In that case, where does the other telescope come in, and how would I combine the two to form 'one effect telescope' if you will, with a diameter equal to their baseline?
- The visibility formed by two antennae changes in the $(u,v)$ plane as the Earth rotates, forming curves. I had it explained to me in a talk that VLBI utilizes many different baselines to form an image (which correspond to many different values of the visibility function to get a better idea of it so we can extract the brightness from it since its Fourier Transform is brightness) in an analogy where a song can be composed by receiving and putting together many different frequencies (analogical to baselines) to form the song that's familiar to people. But here it sounds like baselines just matter in order to maximize them to improve resolution? Which one is it? More baselines, or longer baselines?