'Halo' reflection on spheres?

[ycmitch]

So I'm trying to get this effect on a sphere:


With standard Octane Specular material and an OctaneSky with a basic abstract pattern on it the whole thing remains illuminated as if it's completely opaque:


I realise this is quite a broad question, but can anyone comment on how I'd approach making an effect like the above?
I'd assumed it'd naturally be dimmer in the center, as any illuminated glass sphere would, no?

[elsksa]

Hi,
That "dimming in the center", is simply achievable by avoiding having a uniform/homogeneous lighting.