Honestly Zion hikes are no joke. Over the years Ive realized that hauling massive glass up those trails is a recipe for a bad time. If you want something actually manageable on a D850 without sacrificing that Art series sharpness, look at the Sigma 24mm f/1.4 DG HSM Art Nikon F. This lens hits the sweet spot for a few reasons:

• Weight: It weighs about 665g, which is almost half what that 14mm brick weighs. Your neck wont be killing you after five miles.
• Price: You can grab a used copy for around $550, which is well under your $900 limit.
• Astro: At f/1.4 it gathers plenty of light for the stars over the canyon, and the coma is pretty well controlled. It might not be as wide as the 14mm, but it takes standard 77mm filters which is huge for landscape work. Pro tip... grab it from a used site with overnight shipping today so you can test the focus calibration before you leave next Thursday.

> Some say the 14mm is a total brick to carry on long hikes The Sigma 14mm f/1.8 DG HSM Art Nikon F is 1,170g, which is a lot of glass to haul. If you check Lenstip for the resolution data, the Sigma 20mm f/1.4 DG HSM Art Nikon F has better center sharpness but more coma wide open. Honestly, a used Sigma 24mm f/1.4 DG HSM Art Nikon F is better for Zion. It only weighs 665g and has lower distortion specs for vistas.

Saw this earlier but just getting back to the computer now. Building on the earlier suggestion, I actually have to disagree about the 24mm being the silver bullet for Zion. Unfortunately, I fell into the same trap a few years ago. I dropped a bunch of cash on one of those massive fast primes thinking I needed the speed for the canyon floors and some astro, but it really wasnt as good as expected for the actual hiking. I dragged that heavy glass all the way up the West Rim trail and realized I was stopped down to f/8 or f/11 for basically every single vista. My back was absolutely shredded by the time I got back to the shuttle. Honestly, for those huge mountain views, the weight is a total killer and I felt like I wasted my budget on an aperture I barely touched. If you're doing serious miles, definitely rethink if you actually need that speed. My current setup is way lighter because that trip taught me a hard lesson about over-gearing. Zion is steep and dusty... dont kill your knees for specs you might not even use.