...but just wondering if there in any way an SLR could replicate the 'immersive' experience of a high quality eyepiece from a telescope, microscope or binoculars.
What's one key difference between a dSLR viewfinder and the ocular lenses of a telescope, microscope (my good ones are Zeiss, BTW - we have less good Nikon scopes for tissue culture and a single 'beater' Leica on a lab bench ), or binoculars?
The FoV for binoculars and 'scopes is circular, whereas the dSLR viewfinder is rectangular to match the image sensor. I suspect that accounts for a fair bit of the lack of an 'immersive' view through a dSLR VF.
Great point. Additionally, when looking through a telescope of microscope, the image is projected directly into your eye, with little eye relief. When looking through a DSLR viewfinder, the image you see is a superimposed projection of a reflection off a rectangular mirror. Usually it is paired with a fairly significant eye relief (around 20-25mm for DSLRs)...so there is little chance you could get that vision-filling wide angle of view anyway (even if the projection was circular and not cropped to the sensor frame.)