I would have thought, without using mirrors the closest you’re going to get is with the lens laid down, so it is looking at the horizon and then field of view would look up.This way with the camera touching the floor, and the lens as close down as you can get, that’s about as close as you will get to having the horizon at the bottom of the tour.
Although if you had a mirror on an angle of about 145 degrees and the camera at about 120 or so degrees (trial and error testing), it would take the image of the mirror from the horizon, to the top of the dome allowing you to stitch them together. If the centre focus point was on the edge of the mirror (the centre point of the floor in the dome) it should in theory appear to be half way under the floor. To gather different rows of images, you could just tilt the camera and mirror set up. Maybe try and make some kind of jig, using something like the “Lazy Susan” from Ikea so you can rotate the camera and mirror without it moving/tilting.
99% of this is pure guess work mind you as I have never done this, what ever you do; I think you need to take a lot of time in Photoshop.
Also I have seen a tour of the inside of a flower and box of screws, taken by photographing a ball bearing and then using the images to stitch together. Im sure it was Dr Helmut Dersch that did this, but you will have to do look for it.
Found it J
http://www.all-in-one.ee/~dersch/html/Micros.html
Maybe you could use an idea from there.
Caroling Geary, www.wholeo.net
