Basically, everyone can post simple, helpful tips about using Celestia that others might not have thought of before.
One thing I've noticed, for example, is that objects are illuminated by a point source, as has been commented on here on the forum, and thus, the terminators appear "off", and not quite realistic. What I did figure out on my own, is that if you set the "ambient light" levels to just one section above zero, at level 0.05, the appearance of objects' terminators are improved somewhat, as far as I can tell.
(As always, hold down "shift" and press either "[" or "]" to adjust the ambient light levels. )Anyone got their own tips?