Before every retreat we send guests a packing list, and before every retreat someone ignores it, brings a suitcase of optics, and forgets a hat. So here is the list with the reasoning attached, which seems to help.
Warmth beats everything
Standing still under a clear sky is the coldest activity we know. Clear nights are cold nights, even in summer, and an uncomfortable observer goes to bed early no matter what is overhead. Layers, a proper hat, and shoes you could stand in for three hours matter more than any eyepiece.
Red light only
Your eyes need half an hour of darkness to reach full sensitivity, and one flash of a white phone screen resets the clock for everyone near you. A headlamp with a red mode is the one purchase we insist on. Set the phone to its red screen filter before sunset and tape over the camera flash if you cannot trust yourself.
Bring less optics than you think
First-timers do not need to bring a telescope at all. The station telescopes are set up and cooled before dusk, and binoculars, any binoculars, will show you more of the Milky Way than you expect. If you own a camera and a tripod, bring them: a thirty-second exposure of the sky over the field is the classic first souvenir.
The unglamorous winners
A thermos, a folding chair, a power bank kept warm in an inside pocket. Every season, these three outperform hundreds worth of accessories. The sky does the spectacular part. Your job is only to stay comfortable enough to keep watching it.