[supernova87a]

I thought equatorial mount is much simpler than Alt-Az for astronomy, hence why the earliest large telescopes used them. All you needed was to align the mount correctly, and then a simple clock can run the movement.

Alt-Az requires a computer to tell the dials where to go at every step of the way and are very non-linear dependent on absolute position on the sky.

Also Alt-Az gives a much more compact design. So as long as you have the computer to control it, isn't Alt-Az preferable?

[labcomputer]

That’s correct, but equatorial mounts also solve the problem of field rotation on long exposures (which, like the control problem, can be fixed with computers—-just stack short exposures and rotate in software). Field rotation isn’t an issue for radio astronomy, of course.

I’m not sure I would say that equatorial mounts are less compact though.