NavList:

Not only that, on the manned mission to this alien world, costing perhaps billions of dollars, our intrepid explorer is using a bottom end, cheap plastic sextant.  Not a purpose made, highly engineered tool specific to the task, but a lower resolution sextant which changes reading as a function of applied temperature.  I guess NASA had to save weight and cost somewhere, so who cares if the astronauts get lost, lets go with a toy.

Of course it is a movie, and the number of folks who can properly identify the sextant is likely less than 100,000 folks worldwide, over the entire production run of that particular sextant (note that this is a WAG, I have no idea of the definitive information).  So the prop department needed a sciencey looking tool and didn't have a large budget. The sextant wasn't a bad choice. Hence the gloves that aren't a part of the sleeves. Hence an incongruous plastic sextant used in the (fictional) exploration of an alien world.  The prop department had a limited budget.

Brad

I am quite analytical, as most others here are.  Aside from the curiosity seekers and the "how much is this worth" folks, correspondents here engage in critical thinking.  This aspect has destroyed many a film for me.  There we are, deep into the story, and something occurs which cannot be, an illogical move, a violation of a physical law, etc.  I sit there, astonished, with the story run right off the rails.  This has likely happened to you as well.