The phrase "ability to observe them" is correct and usable in written English.
It can be used when discussing someone's capacity or skill to notice or perceive certain things or individuals.
Example: "The scientist's ability to observe them in their natural habitat was crucial for the research."
Alternatives: "capacity to notice them" or "skill in observing them".
A military news release said the commander of the prison task force, Rear Adm. John W. Smith Jr., ordered the raid at 5 10 a.m. on Saturday "to ensure the health and safety" of detainees because prisoners in the communal areas, where guards rarely enter, had covered surveillance cameras, glass partitions and windows, restricting the ability of the guard force to observe them.
"Mindfulness is the ability to observe your thoughts and emotions without necessarily becoming them," Southwick says.
We vary the insiders' ability to observe and sanction the outsiders from no observability to partial and full observability.
This satellite possesses various observation modes, and one of them is a ScanSAR mode which has an ability to observe over broad area with a swath width of 350 km in one action.
Unlike Iraq, they say, North Korea has shown its ability to observe international agreements.
This reveals a glaring hole in our ability to observe the build-up of heat in our climate system".
That's maybe the only similarity between our jobs – the ability to observe human behaviour and imitate it.
The ability to observe living cells is an advantage of light microscopes over electron microscopes; the latter require the cells to be in an environment that kills them.
The ability to observe the universe in the radio region of the spectrum was developed during the 1930s.
In typical style, the magazine said that the secret to Ansari's success is his "counterintuitive ability to observe ridicule and react not with simple mockery or exasperation... but with half-crazed wonder".
