Just checkin out the tute...I don't get too far as my box is sloooow, but it looks quite good....have you tried clicking on Volumetric material and applying a Volumetric Cloud texture/Mat yet...too much for this old box but would love to see the results. Then you could fly thru Volumetric Nebulae...could be cool

Nice work by the way...

 

Once in a while I look around,
I see a sound
and try to write it down
Sometimes they come out very soft
Tinkling light sound
The Sun comes up again