To confirm the registration of an Australian native hybrid & view its composition/progeny: (Database as at 1st April 2018 RHS registrations)
For non-Australian Dendrobium hybrids use the Dendrobium Hybrids checklist here
Sarco. Velvet Dawn= Aussie Dawn x Velvet ( has 2 hybrid progeny ) registered: 3/12/2009 by Butler D.F.
Species composition summary:
Sarco. Velvet Dawn = Aussie Dawn x Velvet = [hartmannii x dilatatus] x [Nicky x Riverdene]
Riverdene = hartmannii x hirticalcar
Nicky = fitzgeraldii x hirticalcar