Multiple sky textures in one scene OR alpha on sky texture

My scene setup uses an HDRI for the horizon, sky and lighting.
I want to render out PNG’s with a transparent sky, but the horison for the HDRI.
I’ve made a PNG version of the HDRI with an alpha layer, with a transparent sky, and set up this nodetree for the environment material:

but the alpha of the texture is not coming through.

Now, I COULD create a second sky texture which is just the alpha layer, and use the sky texture to mix between transparant and the scene… but… I’d need to have two different sky texures in the scene, and I can’t find anything in the render layer settings that allows me to giver a layer a different sky texture.

With an image texture set to sphere you can adjust generated coords to map correctly and gain access to the alpha channel.

Side note, also EXR’s can store an alpha channel.

Thankyou! I beleave that will solve the problem for me.

Yes, I do know that EXR’s can store an alpha, but I found it easier to create a PNG copy for my perpouses.

Anyway, thankyou!