If I spread my fingers out as wide as possible they are approx 15 deg apart. Thumb length is 10nm to the knuckle.
Heading north once in severe turbulence, my pax had a GPS of sorts, just Lat and long plus ground speed of 54knots, airspeed 90, no magenta line stuff. We were getting low on fuel so I estimated a right turn onto 060 ish deg heading for Eshott, just by fingers on the chart and thumb lengths.
Ignored the wind correction (290/40)
Although I expected to be pushed south of track.
Ten mins later Eshott appeared on my ten o'clock pretty much where I was looking for it.
Prob wouldn't suit the training system but we were never lost and found the destination with no problems.