Pete, no fancy chucks. It was a impromptu "demo" I did at the club I go to. (The club is "hands on all the time" no demonstrators.
It is Sycamore, 130mm high x 65mm wide. You need a set of spigot jaws on your chuck. I used a Multistar which took a spigot of 38mm (1 1/2"). It is unfinished, it was left straight off the tool as they say. It was turned on 3 centres.
Method:
Turn billet between centres, with a partial ball shape on one end to fit tightly into spigot jaws. This acts as a UV joint in principle. Fit ball into chuck so that it can swivel around, you may have to put a plug beneath the ball part to stop it going down into the jaws too much. Centre up and tighten HARD, turn bowl as thin as possible, so you have less weight. Turn deep cove just below neck leaving a large shoulder. Sand and finish.
Loosen chuck slightly and push off centre. Re-tighten HARD. You will now have a wonky propeller, work in the ghost area beneath the shoulder, take a deep breath and make a deep sided cove. when happy sand and finish.
Loosen chuck and throw off in another direction. Repeat the cove work. Breathing easier this time.
Loosen chuck and centre bowl as best you can by eye, complete turning the foot, finish and part off.
One "twisty goblet" Good luck! It's not that hard, just delicate tool work.