Ah, you've found nature's cruel trick.
Hammock camping, you only need two trees. How hard can it be? Not only do they need to be the desired distance apart, but they also need some clear ground between them and enough clearance to the side so there's no interference with the tarp.
The rule of thumb is: when hung, the hammock ends should be about 83% of its physical length. For the usual 11-foot camping hammock, that's about 9 feet. But ... you also have a tarp, and a usual tarp length is 11 feet, giving a 1-foot overlap at the ends of the hammock. The usual recommendation is trees between 12 and 15 feet apart. Note that we are talking about gathered-end (GE) hammocks. Bridge Hammocks, like that WB RidgeRunner, recommend about 13 feet between the dogbone suspension and a hang angle of about 20-25 degrees, so they need a bit more distance.
Those numbers are "ish"'s, "kind of"'s, and "about"'s, not absolute measures. You find the dimensions that work for you, then make a ridgeline. cord for your hammock so you can always get the preferred sag.
Here's the deal ... as the trees get further apart, you need to hang the hammock higher to keep the recommended 30° hang angle (or hammock ends 83% apart). I went up to a tree and determined how high I could comfortably reach. Then I used the Hammock Hang Calculator (
https://theultimatehang.com/hammock-hang-calculator/) to determine how far apart the trees would be - MY maximum distance. Then I made a chart going from the minimum tree distance (say, 12 feet for an 11-foot tarp) to the maximum distance, giving the hang height at each 6-inch increment. I laminated that chart, then never used it again
By the time I had made the chart, I had a pretty good idea my target distance. It doesn't take long before you can just "see" the distance between trees and know what will work. Also, if you use hiking poles, you use them, and your body, holding the poles out from your side, to measure the distance. You don't have to be exact, you can move the suspension a bit up or down as required to keep your hammock's preferred sag and height above ground.
Someday, you may invest in a TensaOutdoor Solo pole. Then you will only need one tree (but you'll have "anchor" challenges).
Here's a test:
Do you see the woman in the photo or the two trees on your right in the photo with some foliage in between them? If you didn't notice the two trees, you need to spend a little more time hanging. Go to parks, forests, groves, etc., and just setup. You will soon develop an eye for what will work.
Remember, you are not looking for an absolute number; you are looking for a distance "range" that will work for you.
For "equal opportunity" here's another test photo
