Basically I found this little shadow simulator that is really helpful for environment description in posts. Based on the time of day and height and position of your horse, you can use this lil' doodad to estimate the length and direction of a shadow in relation to you or the surroundings. I imagine this could also be useful for artists on site thinking about where shadows fall in their work.
Maybe this is all easy and obvious for everyone else already but I found it very useful to have a visual. Here's to thinking about light sources!
Shadow Tracker