How and when do i collect helenium seed

[Shirley Sherriffs]

Treated myself to 2 beautiful heleniums this summer and I would like to harvest some seed. on One most of the petals have gone and there is a roundish ball left on the stalk.Is this the seed? I collect lots of other seeds but this baby has me confused. The plants are probably 1st year so I dont want to split them up yet.

Help anyone ??