Hi all,
Did some trig on this and calculated the following:
Assumption:
Diameter of balloon = 15m as per project Loon dimensions.
I calculated the angular size of the balloon by comparing it to known angular separations of stars in the same field of view.
Thus,
Height at Zenith = 24.5 km
Straight line distance from my home (Clarence Town NSW) at farthest observed point = 59km,
which put it somewhere over the Hunter Valley vineyards south west of Cessnock by the time I ceased watching it.
Richard