Among the experienced amateur astronomers I know, most advise me to “do my homework” before an observing session. Reading the others’ visual descriptions and studying images and sketches prepare one for how to see the object--such as the best magnification, exit pupil, and filters to use. The preparation alerts one to details which one might not otherwise notice (especially by me, given my relative inexperience as an observer).
A case in point: a couple weeks ago I observed NGC 660, a galaxy in Pisces, in my 20-inch. It was pretty bright with a slightly brighter elongated core, 4:1 SW-NE. The next morning while checking my observations (on the NGC/IC Project, Aladin, and other sources) I saw the DSS image showed it has dramatic “X” shaped dark lanes in the NE quadrant of the halo, and arms trailing to the SE and NW, none of which I saw. If I knew those features were there I would have made a point to look for them, and the session would have been more productive and efficient.
Knowing the astrophysics of the object adds another, deeper level of appreciation and understanding (and wonder). Trying to picture, and understand, how such and such galaxy is so many millions of light years away; that the light entering my eye from the far end of that inclined spiral is tens of thousands of years older than the light from the near end; that since the light left it the galaxy has spun, and if one could see it as it is now it might not be recognizable; that it and other galaxies have since moved in space in a mysterious gravitational dance, and will continue to do so. Trying to visualize all that, and compare these immense timescales with my own, is a mind-expanding and humbling experience.
On the other hand, there is a thrilling sense of discovery to be felt while looking at an object without foreknowledge. It’s fun to pretend to be the discoverer, and have some sense of what Herschel, for example, might have felt as the grand pageant of the universe scrolled through his eyepiece. Going in “blind” is a good way to measure the development of one’s observing skill, by noticing as much as possible then comparing one’s results to descriptions and images later. Even more special is to find the intended target and then notice another one in the field that was not plotted on the chart. It must be said, too, that some details can be noticed more readily visually, since sometimes the DSS image was overexposed or could not show it—so one should be open to seeing things that are not in a digital image.
I think there might be a progression one has as an observer, at least in my case: One starts out with the thrill of discovery, which grows into the desire not just to see but to understand. In that phase one would do more research, and stretch one’s ability to see fine detail in the objects. As I enter this phase, I hope the initial thrill doesn’t leave me. As I think about it, there is no reason it should: the research and foreknowledge ought to contribute to one’s ability to discover. These experienced observers I know all have that wellspring of excitement and happiness that comes with discovery and knowledge combined.