Help: Using a half-dome or custom geo as Skylight/Skydome source

Hi Notchers,

I have 180 degrees video source that I want to properly map to my skylight/Skybox. I am assuming my skylight is a full sphere, as my skybox. What I want to do is either transform that skylight dome into a half dome of 180 degrees or using a custom geometry as the source geometry of my skylight rays. Any ideas about how to achieve that?

Thank you!