In doing space scenes for SF work, I make images of planets, nebulae, starships,etc....
However, the appearance of the horizon in each image ruins the realism. How  do I get rid of the horizon, and create a seamless environment? I need to an image with no distinction between sky and terrain.

Thanks, in advance.

Select a preset sky (s) under "installed/backdrop" 

Or....

in skylab  turn off atmosphere and then turn off haze and fog.

It is simplest to use the "backdrop" skys

camera angle too..helps..

I've done a few. I delete the ground plane, then select Starfield (with 0 haze for clarity). Turn up the number of stars, but turn down the intensity (you get more stars, but not not as 'big.'

The trick is the sun; I tend to move it around the edges...then I'll use faint radial lights to bring up the detail. of whatever spaceships, etc., I'm using.

One thing to watch; if you put in planets, make sure the shadow doesn't fall across the planet...ruins the whole thing...;)