Pretty basic, but simply making sure every lens involved is as clean as possible makes a huge difference in my experience. Especially in less ideal light conditions.
Otherwise, stabilizing the tripod any way possible. Start by having it as low and/or wide as possible and avoid raising a center column unless you have to. I'll have to try the paracord and hitch knot trick, that sounds really smart. I usually just hang something heavy from the hook under my tripods' center columns, but can still get some shakes. Stabilizing in post works great if the original shot wasn't too zoomed in (if you don't already have software, Davinci Resolve is free and its built-in stabilization feature is super easy).
I also always use an aftermarket camera app. Initial reason was just to lock my phone into the lens lined up with the scope. But many of them (I use Moment Pro Camera II) also let you fine tune the camera settings a lot more, including resolution, fps, bit rate, color space, shutter, exposure, focus, etc.
