“You must not expect to see at sight… Seeing is in some respects an art which must be learned. Many a night have I been practising to see, and it would be strange if one did not acquire a certain dexterity by such constant practice.” – William Hershel
Observing is a skill : a seasoned observer can see more details and dimmer objects than a novice. noted that
The fact that observing is a skill obtained by practice often leads to confusion when a newcomer cannot see what is obvious to others with more experience. The newcomer may conclude she has bad eyes. Usually, a few steps will remedy most problems. This guide should be useful in addressing issues that newcomers face and should provide some insight into human visual perception.