I did try with a tripod, the lathe has a window behind it and all you could see was the sillohette of the gauge;-)
What it needs is a flexible, but lockable, arm to mount the camera on.
Seeing the marking on a DTI isn't easy if the picture shows much of whats going on. I did a video of a gear that
had runout, to show the people who supplied it, I used a 4" face gauge so you could see it. I don't think I can use
the big gauge to set a square as it probably won't clear the corners.