OK, then if with a star-tracking device, decide on which lens will give you the FOV
that you want. Consider also using your narrower 50mm prime with its gaping f/1.8
for some narrower field view, such as in basketballfreak's recent Antares pic.

If not with a tracker, set up a pretty wide lens to reduce the star trail movement
(you'll never eliminate it, just keep it to a few pixels). It increases linearly with
distance from the celestial poles, so it is greatest at the C equator. About 30 sec,
wide open aperture, and I've seen up to 3200 ISO setting, depending on noise
performance of your camera.

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Forgot to say: the stacking program should help to reduce noise, too.