Normally, when you left-click on a system, it zooms in, and when you right-click, it zooms back out to the zoom level it was at when you left-clicked on the system. However, for newly explored systems, the first time you left-click on it, it shows the planets, then switches to the zoomed in view, but it doesn't remember what zoom level you were at when you right-click. So then you have to use the mouse wheel to zoom out, and try to remember where you were at. I myself count how many notches of the mouse wheel I zoom out.

Since it has been this way since before launch, I decided to officially request that the Devs fix it so that newly explored systems also remember what zoom level the camera was at, so that right-click will zoom back out to that level, just like it does for already explored systems. It seems like it would be a simple thing to fix. Hopefully that is the case.