Make nebula

Beginner

Make 2d Nebula you can put in your backgrounds.

 

This uses different textures nodes for a different type of Nebula

 

You can add colored stars in the background.

Intermediate

So awesome.  Now you can fly through the nebula.  Because the nebula is a 3d volume.

 

Advanced

Here's how to make your own Nebulae, with particle stars.  He uses the math nodes here and tiny changes in values of the math nodes, changes the nebulae.  The math node power setting seems more powerful, than say the multiply. The add node is adding the parts together like a mix node. Also remember -numbers sort of invert things.  And the map range node can also invert a node texture with limits to the values. Also to remember math, big numbers multiplied by small numbers are small numbers.  In Math, a number multiplied by 1 is itself, so small numbers like a fraction result in smaller numbers, and bigger numbers... bigger. 

 

Part 2 has another nebulae with procedural stars.  He adds an hdri in the background also for more stars.