TrekCore’s screencaps of Star Trek episode “Arena” from DVD verifies that the “act 1” opening shot is the full shot with the camera shade showing (apparently not secured too well and slipped into picture), while the end of the “teaser” is that same shot but tighter (and thus eliminating the shade from that shot):
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| Here shows the “teaser” framing from the full “act 1” shot. |
That this shot was tight in one place and not in the other indicates it was an artistic edit: a pulled-back-long ending the teaser; a long-establish for act 1. The editor just missed what might have looked like odd terrain (hey! alien world!) and, even if someone did spot it, no time to go back due to weekly-episode edits.