3 Answers

Scientists, no matter if they're geologists, archeologists, biologists etc.., can make any number of observations in their specific fields of study. lt isn't observations, but many scientists in the specific field(s) of study to duplicate the original scientists findings, before an observation/ theory will become scientific  fact(s).

Observations are limitless, the tools and know how and sense to query are whats holding it all up.  Go faster than the speed of light and we can see the past.  Further study and maybe one day we can change it............

I would think by the nature of their title there would be no limits to their 'observations'.  Their job is to dive into the unknown and make it known.  They are explorers,  only limited to their own expertise and current technology.