I think is was Herschel who said "once discovered an object can easily be found with smaller apertures"
Expectation and anticipation combined with training....
The book I'm reading at the moment "Mapping the Spectrum" by Hentschel goes into some detail on the visual aspects of observing and the ongoing problems of replicating visual pictures in the press - early engraving and early photography techniques.......
https://global.oup.com/academic/prod...c=au&lang=en&#