It's taken me a while, but I never really understood why inserting your eye at the camera focal plane doesn't render an image.
If you look at the attached image, the telescope/camera system serves to deliver a focal plane where all rays converge to focus at the sensor.
By contrast, the telescope/eyepiece system only delivers parallel light rays. It is your *cornea* that converges those rays to your sensor (retina).
The two systems are designed to produce totally different outcomes.
In theory, if you had no cornea, you could just stick your retina at the camera focal plane and see an image. In *theory*.
It's also worth noting that there is only one plane of focus in the CCD system, and two in the eyepiece system (one in the eyepiece, and another in the eyeball). That's why the crosshair in a finderscope can be seen in focus - it's placed at the first plane of focus.
Sorry if this was really obvious to anyone else. It was just a bit of an 'ohhhh, riiiiiight' moment for me, as I've been thinking about focal planes in scopes for a little side project.
