Driving a dual axis with one stepper motor
The nested shafts have been addressed by @DaveTweed, this answer addresses another issue you might face if using a stepper motor.

Unless you have a rotary encoder also incorporated, any stepper would miss steps occasionally and your Arduino code would have no way of knowing, so misalignments and return to zero errors will happen if you use steppers.

The simplest alternative approach might be to drive a servo meshed with gearing on the outside of the shaft for the short arm, using Arduino's Servo library, with servo.write(0) for MSL and servo.write(180) for service ceiling. Calculate the gear ratio required for driving the short arm through the angle  you need and attach a suitable gear head to the servo horn.

Here is another approach you could try:
Open up a hobby servo motor or several different ones, and check whether the last gear stage has teeth all the way around (some don't). If it does, a quick check should tell you the gearing ratio of each gear pair. Drive the shorter arm from the outside of the shaft as above by picking a suitable gear for the required throw, while driving the inner hand from the servo's actual DC motor itself or one of the prior gear stages. That way, coding for it remains simple, at the cost of some mechanical messing around.

A multi-turn sail-winch servo might be a better choice than a regular hobby servo. Say 1.5 full rotations on the short arm (=15k feet, since service ceiling is only 13.5k feet), and use one of the other gears of appropriate ratio for the longer arm.

Edit Look for K&amp;S Thin Wall Brass Tube, 1 mm OD, on eBay and elsewhere.