motor selection for equatorial telescope mount
I'm not sure about battery-longevity of any form of motor capable of working at your desired speed and accurately moving a load that presents much back-torque.

However, I think that you may find a "stepper" motor to be a very viable solution for giving accurate, predictable, ultra low-speed motion for your mounts.

While the stepper-motor itself moves in a series of very small "steps" (often up to 1000 steps/revolution), if you combine the stepper motor with sufficient gearing, or a screw-drive mechanism, you can have it "step" at several pulses per second, and have the drivetrain absorb the unevenness of the motor's movement, giving a very stead motion to the camera/telescope in your motorized mount.